We are often told by our teachers not to do such things as don't ________ a harmonious society. [ ]

A. come about  

B. make for

C. come up  

D. make up

在发动机曲轴后端部装一个飞轮可以（）。

A.提高曲轴运转平稳性

B.提高发动机功率

C.提高发动机转速

D.减少发动机的耗油率