Text: “Green roofs are often promoted as a simple way of cooling overheated cities. Their performance, however, depends heavily on local conditions. In humid tropical cities, where plants can be kept alive all year with little watering, planted roofs stay markedly cooler than bare concrete. Where summers are long and dry, the picture is different: unless they are irrigated, the plants wither in exactly the months when cooling is most needed.”
Why does the writer mention humid tropical cities?
- A to show that green roofs are cheapest where water is scarce
- B to illustrate that the benefit of green roofs varies with climate
- C to argue that concrete roofs should no longer be built
- D to prove that green roofs cool cities in all conditions
Answer: B. The example follows the claim that performance “depends heavily on local conditions” and is paired with a contrasting dry-climate case, so it illustrates that claim. A is a distortion: the text links little watering to humid cities, not to places where water is scarce, and cost is never discussed. C is not stated. D reverses the point, and prove and all are too strong.