2023 CSAT — Q32

Locate. This question asks for the central idea — find the claim the whole passage supports. The passage: source segregation is rare; recycling is informal; most of the municipal budget goes to collection/transport, leaving little for processing; then — “where does waste-to-energy fit?” — “ideally it fits in the chain after segregation… and before the landfill”; the right technology depends on the biodegradable fraction (a little over 50%), for which biomethanation “offers a major solution.” The load-bearing point is the placement of waste-to-energy in the chain: segregation must come first.

Test (is this the main idea or a mere supporting detail? then check the qualifier and the direction). (c) “segregation… is the first step in ensuring the success of waste-to-energy plants” captures that placement — and the passage’s opening lament that segregation is rare makes it the binding prerequisite. Test others: (b) “biomethanation is the most ideal way” over-strengthens “a major solution”; (a) “inexpensive” is never claimed; (d) “biodegradable component not adequate” reverses the passage, which says it is “a little over 50 per cent” and biomethanation offers “a major solution.”

Eliminate by anatomy. (a) is out of scope — cost/inexpensiveness is not discussed; (b) is too strong — “most ideal” inflates “a major solution”; (d) gets the direction backwards — it denies the adequacy the passage affirms. The transferable rule for a central-idea question: the crux is the passage’s structural claim (segregation precedes waste-to-energy), not a superlative about one technology or a reversed fact. Key: (c).

“Where does waste-to-energy fit into all this? Ideally it fits in the chain after segregation (between wet waste and the rest), collection, recycling, and before getting to the landfill.” Waste-to-energy depends on segregation coming first; combined with “the segregation of municipal waste at source is rare,” the crux is that segregation is the prerequisite first step for waste-to-energy to work — exactly (c). (b) over-strengthens (“most ideal”); (a) (“inexpensive”) is not stated; (d) reverses the passage (biodegradable is “a little over 50 per cent” and biomethanation “offers a major solution”) → (c).

The passage situates waste-to-energy in a chain: it works only after segregation, collection and recycling, and segregation at source is currently “rare.” The biodegradable fraction (just over 50%) makes biomethanation “a major solution.”

(c) states the crux: segregation is the first step for waste-to-energy success. (b) over-claims biomethanation as “most ideal” when the passage says “a major solution.” (a) asserts “inexpensive,” never stated. (d) says the biodegradable component is “not adequate,” reversing “a little over 50 per cent… a major solution.”

Answer: (c).

The crux is structural, not evaluative: the passage’s organising idea is where waste-to-energy sits in the chain — and the answer is “after segregation,” which, since segregation is rare, makes segregation the binding first step. The distractors test three different failure modes on the same passage: an unstated cost claim (a), an inflated superlative about biomethanation (b), and a reversed fact about adequacy (d). Reading the passage’s chain-placement claim, not its incidental technology mention, lands (c).