Question 3·Hard·Rhetorical Synthesis
While researching a topic, a student has taken the following notes:
- "Blue carbon" refers to carbon captured by marine ecosystems, including kelp forests.
- Marine ecologist Nadine Dupont investigates whether large-scale kelp cultivation can lock away atmospheric carbon.
- Kelp grows quickly and draws down CO2; some biomass can be sunk offshore.
- Critics warn that sinking seaweed in the deep ocean may cause local oxygen depletion.
- A 2023 study found that roughly 20% of kelp-derived carbon reaches long-term deep-ocean storage.
- Some pilot projects attach harvested seaweed to offshore lines for sinking beyond the continental shelf.
The student wants to introduce a paragraph that acknowledges both the promise and the uncertainty of kelp-based carbon sequestration. Which choice most effectively uses relevant information from the notes to accomplish this goal?
For rhetorical synthesis questions, restate the goal precisely (here: “promise + uncertainty”). Then sort the notes into supporting vs. limiting/qualifying details. Choose the option that combines accurate details from both categories without adding recommendations or claiming the evidence is definitive.
Hints
Restate the goal
You need a sentence that clearly shows both a potential benefit of kelp carbon sequestration and a reason scientists are still uncertain about it.
Pick one detail from each category
Use at least one “promise” note (fast growth/CO2 drawdown/locking away carbon) and at least one “uncertainty” note (only about 20% stored long term or oxygen depletion concerns).
Avoid overclaims
Be wary of choices that treat pilot projects or the 20% figure as proof the method already works, or that recommend a course of action not stated in the notes.
Step-by-step Explanation
Identify the required balance
The question asks for an introduction that acknowledges both the promise and the uncertainty of kelp-based carbon sequestration.
So the best choice must:
- Present a reason kelp sequestration looks promising, and
- Present a reason its overall benefits are uncertain or risky.
Match notes to “promise” vs. “uncertainty”
From the notes, promise includes:
- Kelp grows quickly and draws down CO2.
- Large-scale cultivation could lock away atmospheric carbon.
Uncertainty/concerns include:
- A 2023 study found only about 20% of kelp-derived carbon reaches long-term deep-ocean storage.
- Critics warn sinking seaweed may cause local oxygen depletion.
Eliminate choices that omit key context or go beyond the notes
Prefer the option that uses relevant notes to show both sides.
Eliminate choices that:
- Mention only one concern while omitting a major uncertainty from the notes,
- Make an absolute recommendation (like “abandon” the idea), or
- Treat limited evidence (pilot projects or the 20% statistic) as proof the method already works.
Choose the option that most effectively synthesizes the notes
Choice A directly states the main benefit (rapid growth and CO2 uptake) and includes both uncertainties from the notes (about 20% reaching long-term deep-ocean storage and oxygen-depletion concerns).
Therefore, the correct answer is:
Kelp’s rapid growth and CO2 uptake make large-scale cultivation a promising blue-carbon strategy, but the finding that only about 20% of kelp-derived carbon reaches long-term deep-ocean storage and concerns about oxygen depletion make its benefits uncertain.