单选题 下面这道题的出题与解题涉及哪种说明方法? 题目:What does Dr. White say people usually do to make themselves happier? A)Earn more money. B)Settle in an urban area. C)Gain fame and popularity. D)Live in a green environment. 原文:"There could be a number of reasons," he said, "for example, people do many things to make themselves happier: they strive for promotion or pay rises, or they get married