Official ExplanationChoice (A) is not right as if this were the case many people would already be using small cars.
If
choice (C) was correct it would make the conclusion wrong as it states that accidents would reduce but high speed might ultimately lead to accidents.
Choice (D) should be eliminated as the passage does not refer to all the roads but to only those roads that remain overcrowded, thereby implying that not all roads are overcrowded.
The conclusion does not deal with condition of roads, so choice (E) should be eliminated.
Choice (B) is the correct option as the passage says that if only people using car pools were allowed to use these roads the congestion would reduce. So, (B) can be said to be assumed by the passage.
Answer: B