第21题: [单项选择]Stressful environments lead to unhealthy such as poor eating habits, which______increase the risk of heart disease. A. in turn B. in return C. by chance D. by turns 参考答案:A 答案解析:本题考查介词短语辨析。in turn“依次,轮流,反过来”;in return“作为报答”;by chance“偶然,意外地”;by turns“轮流,交替”。句意为:压力大的环境导致不健康的饮食习惯