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CSAT 2025 paper

UPSC CSE CSAT 2025 · Question 3 · Reading comprehension

Which one of the following statements best reflects the central idea of the passage?

Passage—2

The history of renewable energy suggests there is a steep learning curve, meaning that, as more is produced, costs fall rapidly because of economies of scale and learning by doing. The firms’ green innovation is path-dependent: the more a firm does, the more it is likely to do in the future. The strongest evidence for this is the collapse in the price of solar energy, which became about 90% cheaper during the 2010s, repeatedly beating forecasts. Moving early and gradually gives economies more time to adjust, allowing them to reap the benefits of path-dependent green investment without much disruption. A late, more chaotic transition is costlier.

CSAT 2025 · Q3

Reading comprehension Medium

Which one of the following statements best reflects the central idea of the passage?

Answer & explanation

Answer: (d) Timing plays a crucial role in the case of green technology development.

The passage explains that green technology gets cheaper the more it is used, so moving early and gradually brings its benefits without much disruption, while a late, chaotic transition costs more. The conclusion is about when to act, which is why timing is the central idea.

  • ✗ (a) Economies of scale is only one of the reasons costs fall; the passage never calls it 'essential' for the transition. Its conclusion is about moving early, not about scale as a precondition.
  • ✗ (b) Too broad. The passage speaks only of green innovation and renewable energy, not of 'modern technological progress' in general.
  • ✗ (c) The size of economies is never compared. 'Economies' in the passage are those that move early, not large economies with an advantage.
  • ✓ (d) The closing lines — moving early and gradually lets economies 'reap the benefits … without much disruption', and a late transition 'is costlier' — make timing the decisive factor.

Remember · The central idea usually sits in the author's concluding advice; examples such as solar prices only support it.

Question and answer: UPSC's official GS Paper II (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·

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