It is nice to do something for someone else out of the blue and not to expect anything .A

问题补充：

It is nice to do something for someone else out of the blue and not to expect anything .

A. in relief

B. in return

C. in turn

D. in need

答案：

A. in relief

(答案→)B. in return

C. in turn

D. in need

解析：考查介词短语。句意：突然为其他的人做件事而不期待任何回报才是美好的。in relief显著地，鲜明地，浮雕一般；in return回报；in turn反过来；in need需要。其他中学英语常考到的in短语：in advance提前；in all总共；in balance总而言之；in bed卧床；in body亲自；in brief简明扼要；in case万一；in charge主管；in danger处于危险中；in debt负债；in fact事实上；in general大体上；in front在前方；in use在使用中；in particular特别，尤其。故B正确。