2025 CSAT — Q33

Locate. This asks for the central idea, so find what the evidence is marshalled to prove. The passage’s hard data — “Only 16% of the calories fed to chickens are recovered… five to seven per cent in large animals” — all support one point: converting plant food into animal food is grossly inefficient. That efficiency claim is the crux; the anchor is the conversion-rate lines.

Test (thesis-vs-detail + scope-fit). The key must state the efficiency finding without sliding into a policy prescription the passage never gives. (b) — “Animal-based food is far less efficient than grain/plant-based food in terms of production and utilization” — is the crux exactly. (One gap to close: (b) says “production and utilization,” but the hard data is calorie-conversion efficiency. That broader phrasing is not an over-reach — it is licensed by the passage’s opening line on the “inequality in food production and utilization,” which the conversion-rate data then quantifies; the wording tracks the passage’s own frame, not the calorie figures alone.)

Eliminate by anatomy. (a) over-states the case with a claim the passage never actually makes — “urgent need for a public policy” is a call to action the passage never issues; it reports an inefficiency, not a policy demand. (c) over-states the case — “should replace… in our daily diets” is a dietary prescription the data describes but does not mandate. (d) over-states the case — “inevitable in any fast changing society” turns a described pattern into a law of inevitability. Each over-claims past the evidence; the key reports it. Key: (b).

“this conversion of plant-based food into animal food for humans is far from efficient. Only 16% of the calories fed to chickens are recovered by us when we eat them. This conversion rate goes down to five to seven per cent in large animals.” The passage’s crux is the gross inefficiency of animal-based vs plant/grain-based food — exactly (b).

The passage’s spine is an efficiency argument: as societies grow wealthier they eat more animal products, which means grains and legumes that “could feed humans directly” are converted into animal feed — and that conversion is “far from efficient” (16% recovery from chickens, 5–7% from large animals). The crux is the inefficiency of animal-based food relative to plant/grain-based food.

(b) states this directly. Answer: (b).

All three wrong options share one anatomy — they convert the passage’s descriptive efficiency finding into a prescriptive or fatalistic claim (must legislate / must switch diets / it’s inevitable). The crux question rewards the option that stays descriptive and matches the data. When a passage gives you numbers proving an inefficiency, the central idea is the inefficiency, not the policy a reader thinks should follow from it.