Question 157·Medium·Rhetorical Synthesis
While researching a topic, a student has taken the following notes:
Perovskite solar cells achieve power-conversion efficiencies above 23%. They degrade rapidly when exposed to moisture. In a 2021 study, Maria Lopez and colleagues coated perovskite cells with graphene oxide. The coating increased cell lifespan under humid conditions from 500 hours to 4,000 hours (an eightfold improvement). The coating reduced efficiency slightly, from 23% to 22%. Lopez concluded that this trade-off greatly improves the cells’ commercial viability.
The student wants to summarize the main finding of Maria Lopez and colleagues’ 2021 study. Which choice most effectively uses relevant information from the notes to accomplish this goal?
For questions asking you to “summarize the main finding” or “main idea” based on notes, first underline which study or idea the question targets, then list the few most important points about that specific item (what was done, key results, overall conclusion). Evaluate each answer by asking, “Does this capture all of those points in one sentence, or is it just one detail or background information?” Eliminate answers that are too narrow (only one statistic), too broad or off-target (general facts), or that leave out the researcher’s conclusion, and choose the option that is both accurate and most complete for that goal.
Hints
Focus on the right part of the notes
Look only at the notes that describe Maria Lopez and colleagues’ 2021 study, not the general facts about perovskite solar cells.
Think about what “main finding” means
A main finding usually combines what was tested, the important results, and the researcher’s overall conclusion—not just one number or one detail.
Check for completeness, not just correctness
Several choices may be factually correct, but which one includes both the effect on lifespan and the effect on efficiency plus the conclusion about how this affects the cells’ usefulness in real-world applications?
Step-by-step Explanation
Understand what the question is asking
The question says the student wants to summarize the main finding of a specific study: Maria Lopez and colleagues’ 2021 study.
So you are not just looking for any true statement from the notes—you are looking for one sentence that captures the overall result and conclusion of that study.
Pull out the key points about Lopez’s 2021 study
From the notes, identify everything connected specifically to the 2021 study and its result:
- In 2021, Lopez’s team coated perovskite cells with graphene oxide.
- Under humid conditions, the lifespan increased from 500 hours to 4,000 hours (described as an eightfold improvement).
- The efficiency dropped slightly, from 23% to 22% (only about 1 percentage point).
- Lopez concluded that this trade-off greatly improves commercial viability.
A good summary of the “main finding” should combine what they did, what changed, and what they concluded about it.
Decide what a strong summary must include
Based on those notes, a strong summary of the main finding should:
- Mention the graphene oxide coating (the intervention).
- Include the big gain in lifespan under humid conditions (eightfold / 500 to 4,000 hours).
- Acknowledge the small efficiency loss (about 1 percentage point).
- Reflect the overall conclusion that the trade-off helps commercialization.
Any choice that leaves out most of these elements is too narrow to be the main finding.
Compare each answer choice to the required elements
Now match each option to the list of needed elements:
- Choice A: Only talks about the small efficiency decrease. It ignores the huge lifespan increase and Lopez’s conclusion about commercial viability, so it is only a detail, not the main finding.
- Choice C: Describes general facts about perovskite cells (efficient but moisture-sensitive), which is background, not the specific 2021 study’s result.
- Choice D: Mentions the 4,000-hour lifespan in humid air but leaves out both the efficiency change and the commercialization conclusion. Again, it is incomplete.
- One remaining choice clearly states the coating, the eightfold life extension under humidity, the small efficiency loss, and that researchers see this as a worthwhile trade-off for commercialization.
The answer that includes all of these pieces is:
B) Graphene oxide coating extended the operational life of perovskite solar cells eightfold under humid conditions while only marginally lowering efficiency, a trade-off researchers deem worthwhile for commercialization.