CSAT Solved Papers/ 2025/Q51
2025 CSAT — Q51
Passage
It is hard to predict how changes in the climate and the atmosphere’s chemistry will affect the prevalence and virulence of agricultural diseases. But there is a risk that such changes will make some plant infections more common in all climatic zones, perhaps catastrophically so. Part of the problem is that centuries of selective breeding have refined the genomes of most high-value crops. They are spectacular at growing in today’s conditions but genetic variations that are not immediately useful to them have been bred out. This is good for yields but bad for coping with changes. A minor disease or even an unknown one could suddenly rampage through a genetically honed crop.
Which one of the following statements best reflects the central idea conveyed by the passage?
Thinking pathway
Locate. This asks for the central idea, so find what the passage’s facts converge on. The climate risk, the bred-out genetic variation, and the “could suddenly rampage through a genetically honed crop” all point to one thing: our reliance on genetically uniform high-value crops makes the food supply fragile. That fragility is the anchor.
Test (thesis-vs-detail + scope-fit). The key must name the vulnerability arising from dependence on honed crops. (b) — “Our total dependence on genetically honed crops entails possible food insecurity” — states exactly that, and keeps the passage’s hedge (“possible”).
Eliminate by anatomy. (a) offers a supporting detail as the main point — climate’s effect on productivity is the passage’s framing, not its point; the point is the genetic-uniformity vulnerability. (c) is a claim the passage never actually makes and over-generalises — “food security should not depend on productivity alone” is a broad maxim the passage never states. (d) over-states the case — “should be replaced with wild varieties” is a prescription the passage never makes (it diagnoses a risk, not a remedy). Key: (b).
Evidence in the text
“centuries of selective breeding have refined the genomes of most high-value crops… genetic variations that are not immediately useful to them have been bred out. This is good for yields but bad for coping with changes. A minor disease or even an unknown one could suddenly rampage through a genetically honed crop.” The central idea is the vulnerability created by dependence on genetically honed crops — i.e. possible food insecurity (b).
Worked rationale
The passage explains that selective breeding has made high-value crops genetically uniform — great for yields, but they have lost the variation needed to cope with change, so “a minor disease or even an unknown one could suddenly rampage through a genetically honed crop.” The central idea is the food- security vulnerability created by dependence on these genetically honed crops.
(b) captures this. Answer: (b).
Why the other options miss
- A a supporting detail offered as the main point: climate change is the passage’s opening frame, not its core; the core is genetic uniformity and the vulnerability it creates.
- C a claim the passage never actually makes: a broad maxim (“shouldn’t depend on productivity alone”) the passage never articulates.
- D over-states the case: prescribes replacing honed crops with wild varieties — a remedy the passage does not propose; it identifies a risk.
Specialist insight
The deadly distractor is (a): climate change opens the passage, so a skimmer takes it as the theme. But the passage’s argument is about genetic uniformity — climate is merely the trigger that exposes the fragility. The central idea sits where the evidence converges (vulnerability of honed crops), not at the opening frame. (b) also correctly preserves the author’s “possible” hedge, where (d) over-commits to a fix.
(a) mistakes the climate-change framing for the thesis; the core is the food-insecurity vulnerability of genetically honed crops — (b).