It is the first time that he ______ here and now it is high time that he ______ around.

A．come; should be shown

B．has come; was shown

C．came; was shown

D．has come; be shown

铁路上常用的圆形涵洞根据基础的设计可分为有基管涵和()。

A.无基管涵

B.桩基管涵

C.扩大基础管涵

D.异型基础管涵