Question 3·Hard·Rhetorical Synthesis
While researching a topic, a student has taken the following notes:
- Carbon nanotube (CNT) membranes mimic the water channels of aquaporin proteins, letting water flow rapidly while blocking salt ions.
- A 2023 study by the U.S. National Renewable Energy Laboratory (NREL) found that CNT membranes use about 70 percent less energy for desalination than conventional reverse-osmosis.
- CNT membranes are currently costly; work is under way to cut prices through roll-to-roll fabrication.
- A United Nations report warns that by 2030 global freshwater demand could exceed supply by 40 percent.
The student is drafting a brief statement for a city council meeting to persuade officials to fund research into CNT desalination. Which choice most effectively uses relevant information from the notes to serve this purpose?
For rhetorical synthesis questions, start by underlining the purpose (inform, persuade, propose, etc.) and the audience in the prompt. Then scan the notes and quickly separate the information into: (1) details that show the problem or need, (2) details that show the benefits or potential, and (3) extra technical or background facts. Choose the answer that (a) directly matches the stated purpose and audience, (b) uses the most relevant notes (usually combining problem + benefit + any key limitation), and (c) avoids unnecessary technical detail that doesn’t strengthen the argument for that specific task.
Hints
Clarify what the statement needs to do
Focus on the goal: the student wants to persuade city council officials to fund research. Which kinds of details would be most convincing for that purpose?
Decide which notes are most relevant
Look back at the bullet points. Which ones describe a big problem and a strong benefit, and which ones are just technical descriptions or process details?
Look for a choice that connects multiple ideas
Which answer choice brings together more than one of the key ideas (problem, benefit, and current limitation) rather than focusing on just one detail?
Step-by-step Explanation
Understand the task, purpose, and audience
The question asks for a brief statement for a city council meeting to persuade officials to fund research into CNT desalination.
So the best sentence should:
- Be persuasive, not just descriptive.
- Make it clear why CNT desalination research is worth funding.
- Use information from the notes that shows both the problem (water shortage) and the value of CNT membranes.
Identify the most persuasive notes
Look at which notes most strongly support funding research:
- A global problem: "By 2030 global freshwater demand could exceed supply by 40 percent." This shows urgency and need.
- A key benefit: "CNT membranes use about 70 percent less energy" than conventional methods. This shows efficiency and advantage.
- A barrier: "CNT membranes are currently costly; work is under way to cut prices." This shows why more research funding is needed.
The note about mimicking aquaporins is interesting but mainly technical, not directly persuasive for funding.
Check which option best combines problem, benefit, and need for research
Evaluate how each answer choice uses the notes and serves the persuasive purpose:
- One choice only explains how CNT membranes work.
- Another gives just the energy statistic, with no mention of the water crisis or need for research.
- Another focuses only on lowering costs, without stating why the technology matters.
- Only one choice ties together:
- the serious global water shortage,
- the energy-saving advantage of CNT membranes, and
- the fact that they are still expensive, implying research is needed to make them practical.
That comprehensive, problem–solution–obstacle structure makes the strongest argument to a city council deciding on research funding.
Select the choice that best matches
The answer that combines the global 40 percent freshwater gap, the energy-saving benefits of CNT membranes, and their current high cost—clearly supporting the argument for funding further research—is:
C) Although still expensive, energy-saving carbon nanotube membranes may help close the looming 40 percent gap between global freshwater demand and supply.