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
网友回答
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。