— I hear it will rain tomorrow.

— It _____ true. You see, there are so many black clouds in the sky now. [ ]

A. won't be

B. will be

C. may be

D. may not be

机械零件的结构工艺性是指所设计的零部件在保证产品使用性能的前提下，能用（）的方法制造出来。

A.生产率高

B.劳动量小

C.生产成本低

D.A、B、C