Mark Scheme

Section A — Structured Questions

Question 1 (12 marks)

(a) (i) Temperature (of water) / temperature in °C (1 mark) Accept: independent variable is temperature Reject: heat; warmth without reference to temperature

(a) (ii) Number of bubbles / number of bubbles produced in 5 minutes (1 mark) Accept: bubble count; rate of bubble production

(b) Any TWO from:

• Same/constant light intensity
• Same volume of water
• Same size/mass/length of Elodea sprig
• Same concentration of carbon dioxide in water
• Same time period (5 minutes)
• Same species/type of plant (2 marks — 1 mark each)

(c) Award marks as follows:

• At 50°C, enzymes are denatured/destroyed (1 mark)
• The active site changes shape/is altered (1 mark)
• Photosynthesis slows down/stops (1 mark) (Maximum 3 marks) Accept: enzymes involved in photosynthesis stop working properly Reject: enzymes die/are killed (must use denature/destroy)

(d) (i) Oxygen / O₂ (1 mark)

(d) (ii) Award marks for correct procedure:

• Use a glowing splint (1 mark)
• The splint relights/bursts into flame (1 mark) (2 marks) Accept: insert glowing wooden splint into test tube containing the gas Reject: burning splint instead of glowing splint

(e) Award marks for:

• Repeat the experiment/investigation (1 mark)
• Calculate a mean/average for each temperature (1 mark) OR
• Use more readings at each temperature (1 mark)
• Calculate a mean/average (1 mark) (Maximum 2 marks) Accept: do several trials; take multiple measurements

Question 2 (14 marks)

(a) (i) Sedimentary rock (1 mark)

(a) (ii) Award marks as follows:

• Remains/shells of dead sea organisms/creatures collect/accumulate on sea floor (1 mark)
• Layers build up and are compressed/compacted over long periods of time (1 mark) (2 marks) Accept: calcium carbonate from marine organisms; fossils; coral Reject: rocks are compressed (must refer to layers/sediments/organisms)

(b) (i) Calculation: Mr of CaCO₃ = 40 + 12 + (3 × 16) = 100 (1 mark) Number of moles = mass ÷ Mr = 5.0 ÷ 100 (1 mark) = 0.05 moles (1 mark) (3 marks) Award 2 marks for correct answer with no working Award 1 mark for correct formula (n = m/Mr) even if calculation incorrect

(b) (ii) Any ONE from:

• Fizzing/effervescence/bubbles produced
• Limestone dissolves/disappears/gets smaller
• Temperature increases/solution gets warm (1 mark) Reject: gas produced (too vague); smoke

(c) (i) Any TWO from:

• Destruction of habitats/loss of biodiversity
• Dust pollution/air pollution
• Noise pollution
• Visual pollution/scarring of landscape
• Loss of agricultural land
• Soil erosion
• Water pollution from runoff (2 marks — 1 mark each)

(c) (ii) Any ONE appropriate suggestion with explanation:

• Replant/reforest the quarry after mining (1 mark) to restore habitats (1 mark) OR
• Use dust suppression methods/water spraying (1 mark) to reduce air pollution (1 mark) OR
• Limit mining to certain areas (1 mark) to protect other habitats (1 mark) (2 marks) Accept: other sensible suggestions with appropriate justification

(d) Award marks as follows:

• Limestone contains calcium carbonate (1 mark)
• Calcium carbonate dissolves in water/reacts with water (1 mark)
• Forms calcium hydroxide/alkali solution/raises pH (1 mark) (Maximum 3 marks) Accept: limestone is alkaline; calcium carbonate is a base Reject: limestone is a base (needs carbonate reference)

Question 3 (14 marks)

(a) (i) Small intestine (1 mark) Accept: ileum Reject: large intestine; intestine only

(a) (ii) Award marks for any TWO from:

• Completes digestion/final breakdown of food using enzymes (1 mark)
• Absorption of digested food/nutrients into bloodstream (1 mark)
• Large surface area for absorption (due to villi) (1 mark) (Maximum 2 marks) Accept: nutrients pass through wall into blood

(b) (i) Bile (1 mark) Reject: bilerubin; stomach acid

(b) (ii) Gall bladder (1 mark) Accept: gallbladder

(c) (i) pH 1-3 / pH 2 / acidic pH (1 mark) Accept: pH 1-4 Reject: just "acidic" without pH range or number

(c) (ii) Award marks for any TWO from:

• Kills bacteria/harmful microorganisms in food (1 mark)
• Provides optimum/best pH for stomach enzymes/pepsin to work (1 mark)
• Denatures proteins/begins breakdown of proteins (1 mark) (Maximum 2 marks)

(d) (i) 8 hours (1 mark) Award mark for: 20:00 hours; 2000h - 1300h = 8h Reject: incorrect calculation

(d) (ii) Rectum (1 mark) Accept: anus Reject: large intestine; colon (these process but don't store immediately before removal)

(d) (iii) Award marks as follows:

• Green salad contains fibre/roughage/cellulose (1 mark)
• Fibre helps movement of food through intestine/prevents constipation/adds bulk to faeces (1 mark) (2 marks) Accept: dietary fibre; aids peristalsis

(e) Award marks as follows:

• Removes harmful/contaminated food from stomach (1 mark)
• Before it can be absorbed/cause more harm/make person more ill (1 mark) (2 marks) Accept: prevents toxins entering bloodstream; expels bacteria

Question 4 (14 marks)

(a) (i) Non-renewable (1 mark)

(a) (ii) Award mark for:

• It takes millions of years to form/cannot be replaced once used (1 mark) OR
• Formed from fossil remains over geological time (1 mark) Accept: finite resource; will run out

(b) (i) Balanced equation: CH₄ + 2O₂ → CO₂ + 2H₂O (3 marks) Award marks as follows:

• Correct reactants and products (1 mark)
• Correct balancing of equation (2 marks) Award 1 mark only if equation unbalanced but products correct Reject if incomplete combustion products shown (CO or C)

(b) (ii) Any ONE from:

• Global warming/climate change/enhanced greenhouse effect
• Rising sea levels
• Melting ice caps/glaciers
• Ocean acidification (1 mark) Accept: contributes to greenhouse effect Reject: air pollution (not specific enough); ozone depletion (wrong gas)

(c) (i) Award marks as follows:

• Kinetic energy/movement energy/energy of motion (1 mark)
• To electrical energy (1 mark) (2 marks) Reject: mechanical to electrical without reference to kinetic/movement

(c) (ii) Kinetic energy / thermal energy / heat energy (1 mark) Accept: movement energy; internal energy Reject: steam energy

(d) (i) Calculation: Energy = 450 × 3.6 × 10⁶ (1 mark) = 1.62 × 10⁹ J / 1 620 000 000 J (1 mark) (2 marks) Accept: 1.62 × 10⁹; 1 620 MJ Award 1 mark for correct method shown even if arithmetic error

(d) (ii) Calculation: Cost = 450 × $0.45 (1 mark) = $202.50 (1 mark) (2 marks) Accept: TT$202.50; $202; $203

(e) Any ONE from:

• Solar energy/photovoltaic cells
• Wind energy
• Hydroelectric power
• Wave/tidal energy
• Geothermal energy (particularly relevant to volcanic islands)
• Biomass/biofuels (1 mark) Reject: nuclear (not renewable)

Section B — Extended Response

Question 5 (18 marks)

(a) Explanation of hurricane formation and conditions (6 marks)

Mark allocation:

• Explanation of formation process (3 marks)
• Three conditions necessary (3 marks — 1 mark each)

Level 3 (5-6 marks): Comprehensive explanation showing clear understanding of hurricane formation mechanism with accurate scientific terminology. States three or more correct conditions with specific details (e.g., numerical values for temperature).

Level 2 (3-4 marks): Adequate explanation of formation process with some scientific accuracy. States two or three conditions, may lack specific detail.

Level 1 (1-2 marks): Basic or incomplete explanation. States one or two conditions with limited scientific accuracy.

Creditable content — Formation process:

• Warm moist air rises from warm ocean surface
• Air cools and condenses forming clouds
• Heat/energy is released (latent heat)
• Low pressure area forms at surface
• More air rushes in and spiral pattern develops due to Coriolis effect/Earth's rotation
• Eye forms at center

Creditable content — Conditions necessary:

• Warm ocean water (at least 26-27°C)
• Ocean depth of at least 50-60 m
• Location at least 5° from equator (for Coriolis effect)
• Low wind shear
• Unstable atmospheric conditions
• High humidity/moisture in atmosphere
• Late summer/autumn season

Accept: tropical cyclone; typhoon; descriptions of energy transfer Reject: vague references to "hot air" without mechanism

(b) (i) Causes of earthquakes (4 marks)

Level 2 (3-4 marks): Clear explanation linking tectonic plate movement to earthquake occurrence. Mentions stress/strain build-up and release. Uses correct terminology (fault lines, seismic waves, focus/epicenter).

Level 1 (1-2 marks): Basic description of plate movement. Limited explanation of mechanism. May lack technical terms.

Creditable content:

• Tectonic plates move/are in constant motion
• Plates collide/slide past each other/pull apart at boundaries
• Friction prevents smooth movement
• Stress/pressure/strain builds up along faults
• Sudden release of energy when rocks break/slip
• Energy released as seismic waves
• Waves travel from focus/hypocenter to epicenter

Accept: convection currents in mantle as underlying cause Reject: "plates crash" without reference to friction/stress build-up

(b) (ii) Vulnerability of Haiti and Jamaica (3 marks)

Creditable content (any 3 points):

• Located on/near tectonic plate boundaries
• Caribbean plate meets North American plate
• Presence of active fault lines (e.g., Enriquillo-Plantain Garden fault)
• Historical evidence of major earthquakes in region
• Transform/conservative plate boundary causes shallow earthquakes
• High population density in vulnerable areas
• Poor building standards/infrastructure

Accept: specific reference to 2010 Haiti earthquake Mark generously: for understanding of geographical vulnerability combined with social factors

(c) (i) Effects of volcanic ash on agriculture (5 marks)

Level 3 (4-5 marks): Discusses both short-term and long-term effects with clear distinction. Shows understanding of both negative and positive impacts. Uses scientific reasoning.

Level 2 (2-3 marks): Mentions both short-term and long-term effects but may lack balance or detail. Some scientific understanding evident.

Level 1 (1 mark): Lists effects without clear categorization or limited to one timeframe only.

Creditable content — Short-term effects:

• Ash covers crops/plants blocking sunlight
• Photosynthesis reduced/stops
• Crops die/fail immediately
• Ash damages leaves and stems
• Contamination of water supplies
• Soil becomes compacted/heavy
• Animals cannot graze/feed
• Ash mixed with rain forms acidic compounds

Creditable content — Long-term effects:

• Ash weathers and enriches soil with minerals
• Volcanic soil becomes very fertile
• Better crop yields in future years
• Changes in soil pH (may need correction)
• Land unusable for months/years while ash settles
• Need to remove ash before replanting
• Economic losses affect farming communities

Accept: specific crops (bananas, dasheen, plantains relevant to St. Vincent) Credit: balanced discussion acknowledging both damage and eventual benefit

Question 6 (18 marks)

(a) Life cycle of Aedes aegypti mosquito (5 marks)

Level 3 (4-5 marks): Complete, accurate description of all four stages in correct sequence. Mentions key features of each stage (e.g., larva in water, pupa non-feeding, adult emerges). Includes approximate timescales or conditions.

Level 2 (2-3 marks): Describes three or four stages with general accuracy. Sequence may be correct but lacks detail about characteristics of each stage.

Level 1 (1 mark): Names some stages or gives partial description. Limited scientific accuracy.

Creditable content:

• Female lays eggs in/near standing water
• Eggs hatch into larvae/wrigglers (requires water)
• Larvae feed in water (on microorganisms/organic matter)
• Larvae breathe through siphon tube at surface
• Larvae molt several times/go through instars
• Larvae develop into pupae/tumblers
• Pupae do not feed
• Pupae are mobile/tumble in water
• Adult mosquito emerges from pupa
• Life cycle takes 7-10 days under optimal conditions
• Temperature and water availability affect development

Accept: wiggler/wriggler for larvae; tumbler for pupa Reject: incomplete metamorphosis (must show four distinct stages)

(b) Transmission of dengue fever (4 marks)

Level 2 (3-4 marks): Clear, sequential explanation of transmission from infected to healthy person via mosquito vector. Shows understanding of virus replication in mosquito and injection into new host.

Level 1 (1-2 marks): Basic description of mosquito bite transmitting disease. Limited detail about viral mechanism.

Creditable content:

• Female Aedes aegypti mosquito bites infected person
• Mosquito ingests blood containing dengue virus
• Virus multiplies/replicates in mosquito's body (8-12 days)
• Mosquito becomes infective
• Infected mosquito bites healthy person
• Virus injected through mosquito saliva
• Virus enters bloodstream of healthy person
• Person becomes infected with dengue

Accept: mosquito is a vector; extrinsic incubation period Reject: mosquito "carries" virus without reference to replication

(c) (i) Methods to control mosquito populations (6 marks)

Award 2 marks for each well-described method (maximum 6 marks): Each method should include:

• Clear identification of method (1 mark)
• Explanation of how it controls mosquitoes (1 mark)

Creditable methods:

1. Environmental/source reduction:

• Remove/drain standing water/containers where mosquitoes breed
• Prevents larvae from developing

2. Chemical control:

• Apply larvicides to water bodies to kill larvae
• Spray insecticides (e.g., malathion) to kill adult mosquitoes
• Use insecticide-treated materials

3. Biological control:

• Introduce fish (e.g., guppies) that eat mosquito larvae
• Use Bacillus thuringiensis bacteria that kill larvae
• Release sterile male mosquitoes (SIT technique)
• Use Wolbachia bacteria to reduce virus transmission

4. Physical barriers:

• Use window/door screens to prevent entry
• Sleep under mosquito nets (preferably insecticide-treated)
• Cover water storage containers with tight lids

5. Community action:

• Public education campaigns
• Regular cleanup campaigns/"clean up" days
• House-to-house inspections by health officials

6. Personal protection:

• Use mosquito repellents (containing DEET)
• Wear long-sleeved clothing
• Avoid outdoor activity at dawn/dusk when mosquitoes most active

Accept: specific Caribbean examples (e.g., "clean up your environment" campaigns) Credit: integrated approaches that combine methods

(c) (ii) Evaluation of chemical vs biological control (3 marks)

Level 2 (2-3 marks): Balanced evaluation presenting advantages and disadvantages of both approaches. Makes judgment about relative effectiveness. Shows critical thinking.

Level 1 (1 mark): Lists advantages or disadvantages of one or both methods without evaluation or comparison.

Creditable content — Chemical insecticides advantages:

• Quick/immediate results
• Effective at killing large numbers
• Targets adult mosquitoes directly
• Well-established technology

Creditable content — Chemical insecticides disadvantages:

• Mosquitoes develop resistance over time
• Harmful to other insects/animals/environment
• Temporary effect/requires repeated application
• Health concerns for humans
• Expensive in long term
• Chemicals may contaminate water supplies

Creditable content — Biological control advantages:

• More sustainable/long-lasting
• Environmentally friendly/safe
• Targets specific species
• Mosquitoes less likely to develop resistance
• Can be cost-effective long-term
• No harmful chemicals

Creditable content — Biological control disadvantages:

• Slower to show results
• May be difficult to establish
• Requires ongoing monitoring
• Initial costs may be high
• May not eliminate all mosquitoes
• Some methods (e.g., Wolbachia) are new/experimental

Creditable conclusion/evaluation:

• Integrated approach combining both is most effective
• Biological control better for long-term sustainability
• Chemical control needed for outbreak situations
• Context-dependent (urban vs rural; outbreak vs prevention)

Accept: references to Caribbean-specific examples (e.g., Trinidad's guppy programme; Cayman Islands' Wolbachia project) Credit highly: candidates who recognize that effectiveness depends on context and that integrated management is optimal

Sample Answers with Examiner Commentary

Question 5(c)(i) — Sample Answers

Grade I (Distinction) answer

Volcanic ash has several short-term effects on agriculture in St. Vincent. Immediately after the eruption, thick layers of ash settle on crops, completely covering leaves and stems. This blocks sunlight from reaching the plants, which prevents photosynthesis from occurring. Without photosynthesis, plants cannot produce glucose for energy and growth, causing crops like bananas, plantains, and dasheen to die within days. The weight of the ash also physically damages plants, breaking branches and stems. Additionally, ash mixed with rain forms a cement-like substance that compacts the soil, making it difficult for roots to obtain oxygen and water. Water sources become contaminated with ash, affecting irrigation systems.

However, in the long term, volcanic ash can have positive effects on agriculture. As the ash weathers and breaks down over months to years, it releases valuable minerals including potassium, phosphorus, and magnesium into the soil. These minerals act as natural fertilizers, making volcanic soils some of the most fertile in the world. This is why many Caribbean islands with volcanic origins have historically productive agricultural sectors. In St. Vincent, after the ash is cleared and the soil recovers, farmers may experience better crop yields than before the eruption. The island's banana industry, which is economically important, could benefit from this increased fertility in the years following the disaster. However, it may take 1-2 years before farmers can fully utilize their land again, causing significant economic hardship in the interim.

Mark: 5/5

Examiner commentary: This answer achieves full marks by clearly distinguishing between short-term and long-term effects with excellent scientific reasoning. The candidate demonstrates sophisticated understanding by explaining the mechanism of photosynthesis inhibition, physical damage, soil compaction, and the process of mineral enrichment. The response is well-structured, uses appropriate scientific vocabulary, and includes relevant context about St. Vincent's agriculture. The balanced discussion acknowledging both negative impacts and eventual benefits shows analytical thinking expected at Grade I level.

Grade III (Pass) answer

In the short term, the volcanic ash from La Soufrière has negative effects on farming. The ash covers all the crops and blocks out the sunlight, so the plants cannot make food through photosynthesis and they die. The ash is also very heavy and can break the plants. Farmers lose their crops and cannot harvest anything. The ash gets into water supplies and makes them dirty. Animals cannot eat grass that is covered in ash.

In the long term, volcanic ash can be good for agriculture. The ash contains minerals that are good for plants. When it breaks down, it makes the soil very fertile. This means that crops can grow better after some time. Volcanic soil is known to be good for farming. But it takes a long time for the land to recover and farmers cannot grow anything for a while, which causes them to lose money.

Mark: 3/5

Examiner commentary: This answer demonstrates adequate understanding and gains 3 marks. The candidate correctly identifies key short-term effects (covering crops, blocking sunlight, stopping photosynthesis, physical damage) and long-term benefits (mineral enrichment, increased fertility). However, the answer lacks the depth and scientific precision of a top-band response. The explanation of photosynthesis is simplified ("make food") rather than referencing glucose production. The description of minerals is vague ("good for plants") without naming specific nutrients. The time frame for recovery is mentioned but not quantified. To reach Grade I, this answer needed more specific scientific terminology and fuller explanation of mechanisms.

Grade V (Near miss) answer

The volcanic ash from the eruption is very bad for crops. It covers all the plants and kills them because they cannot get sunlight. All the crops die and farmers cannot grow food anymore. The ash pollutes the water and soil. Everything is destroyed by the ash.

Later on, the ash can help plants grow because it has nutrients in it. The soil becomes rich and fertile from the volcano. Volcanic islands have good soil for farming.

Mark: 2/5

Examiner commentary: This answer achieves only 2 marks. While the candidate correctly identifies that ash blocks sunlight and kills crops (1 mark), and that ash eventually enriches soil (1 mark), the response lacks development and contains imprecise language. The candidate does not explain why blocking sunlight kills plants (no reference to photosynthesis). The statement "everything is destroyed" is too vague. The long-term effects section is extremely brief without explaining the weathering process or naming specific minerals. The answer shows a basic grasp of the topic but insufficient detail for higher marks. To improve, the candidate should explain mechanisms (e.g., photosynthesis, mineral release), use scientific vocabulary, and provide specific examples. The response also lacks clear structure distinguishing short-term from long-term effects.

Question 6(c)(ii) — Sample Answers

Grade I (Distinction) answer

Both chemical insecticides and biological control methods have advantages and disadvantages in managing mosquito populations, and their effectiveness depends on the specific situation.

Chemical insecticides such as malathion or temephos are highly effective at rapidly reducing mosquito populations. When sprayed in areas during a dengue outbreak, they can kill large numbers of adult mosquitoes within hours, providing immediate relief and potentially preventing disease transmission. This makes them valuable during public health emergencies when quick action is essential. However, chemical insecticides have significant drawbacks. Mosquitoes can develop genetic resistance to insecticides through natural selection, as has been documented with Aedes aegypti populations in Trinidad and Jamaica. This means the chemicals become less effective over time, requiring higher doses or different chemicals. Furthermore, insecticides are non-selective and kill beneficial insects such as bees and butterflies, harming ecosystems. They can contaminate water sources and pose health risks to humans, particularly children. The effects are also temporary – once spraying stops, mosquito populations quickly recover if breeding sites remain.

Biological control methods offer more sustainable alternatives. For example, introducing guppies (Poecilia reticulata) into water tanks and ponds, as practiced in Trinidad, provides long-term control because the fish continuously consume mosquito larvae. Similarly, using Bacillus thuringiensis israelensis (Bti) bacteria specifically targets mosquito larvae without harming other organisms. The newer Wolbachia technique, being tested in countries including the Cayman Islands, reduces the ability of mosquitoes to transmit dengue virus and can become self-sustaining in the population. Biological methods are environmentally safe and mosquitoes are less likely to develop resistance. However, they take longer to establish, require initial investment and monitoring, and may not reduce populations fast enough during an outbreak situation.

In conclusion, the most effective approach is integrated vector management that combines both methods strategically. Biological controls should be used for long-term, sustainable prevention, while chemical insecticides are reserved for emergency response during outbreaks. This balanced approach maximizes effectiveness while minimizing environmental harm and resistance development.

Mark: 3/3

Examiner commentary: This outstanding answer earns full marks through comprehensive, balanced evaluation of both approaches. The candidate presents multiple advantages and disadvantages for each method with scientific accuracy and specific examples relevant to the Caribbean context (Trinidad's guppy programme, resistance in Caribbean mosquito populations, Cayman Islands' Wolbachia project). The answer demonstrates critical thinking by recognizing that effectiveness is context-dependent and concluding that integrated management is optimal. The sophisticated vocabulary, logical structure, and evidence-based reasoning exemplify Grade I performance.

Grade III (Pass) answer

Chemical insecticides and biological control have different advantages and disadvantages.

Chemical insecticides are effective because they kill mosquitoes quickly. They can be sprayed in areas where there are lots of mosquitoes and reduce the population fast. This is useful when there is a dengue outbreak and action is needed urgently. However, chemicals have problems. Mosquitoes can become resistant to the insecticides so they stop working as well. The chemicals also kill other insects, not just mosquitoes, which is bad for the environment. They can be harmful to people and animals. The effect does not last long and mosquitoes come back.

Biological control is better for the environment. Using fish like guppies to eat mosquito larvae is natural and does not use chemicals. The fish keep eating the larvae so it lasts longer. Biological control does not harm other animals or the environment. But it takes longer to work than chemicals. It might not kill enough mosquitoes quickly during an outbreak.

Both methods can work, but biological control is probably better in the long term because it is more sustainable. Chemicals are good for emergencies.

Mark: 2/3

Examiner commentary: This answer earns 2 marks for demonstrating satisfactory evaluation of both methods. The candidate correctly identifies key advantages and disadvantages of each approach and attempts to compare their effectiveness. However, the answer lacks the depth and sophistication of a Grade I response. The explanations are somewhat superficial (e.g., "chemicals have problems," "better for the environment") without detailed scientific reasoning. There is no mention of specific biological methods beyond fish, no Caribbean examples, and limited explanation of mechanisms like resistance development. The conclusion is brief and could be more fully justified. To reach the top band, this candidate needed to provide more specific examples, explain concepts like natural selection in resistance, and develop a more nuanced conclusion about integrated approaches.

Grade V (Near miss) answer

Chemical insecticides kill mosquitoes fast which is good. But they are bad for the environment and can poison people. They also cost a lot of money.

Biological control is using natural methods like fish to eat mosquitoes. This is better because it is natural and safer. It does not cause pollution.

I think biological control is more effective because it is better for the environment and safer for people.

Mark: 1/3

Examiner commentary: This answer achieves only 1 mark for basic recognition that both methods exist and that biological control is environmentally preferable. However, the response is far too brief and superficial for a 3-mark evaluation question. The candidate lists simple points without explanation or development. There is no discussion of how effectiveness differs in different contexts (outbreak vs. prevention), no specific examples of biological methods beyond "fish," no mention of important concepts like resistance or sustainability, and no acknowledgment that chemical methods might sometimes be necessary. The conclusion is stated rather than justified through evidence and reasoning. To improve, this candidate must provide detailed explanations, specific examples, balanced discussion of both advantages and disadvantages, and demonstrate analytical thinking rather than simply stating a preference. The answer shows very limited scientific understanding and poor examination technique for extended-response questions.