— I usually go there by train.    

— why not _____by boat for a change. [ ]

A. to go 

B. going

C. go 

D. you go

复合模可以分为哪两类（）。

A.单工序复合模和级进复合模

B.横向复合模和纵向复合模

C.正装式复合模和倒装式复合模

D.卧式复合模和立式复合模