— Alvin，are you coming with us?

—I'd love to，but something unexpected ________.

A．has come up

B．was coming up

C．had come up

D．would come up

用围堰将水工建筑物分段分期围护起来进行施工的方法即( )。

A．束窄河床导流

B．通过建筑物导流

C．隧洞导流

D．涵管导流