Detailed Instructions: You are given a science question (hard-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.
Q: Cities control the amount of pollution that is allowed to come from cars. How does this most likely help people?
(A) The air stays cleaner. (B) Cars can travel at faster speeds. (C) The skills of the drivers improve. (D) It becomes safer to drive on the roads.
A:
A