--_____ to the United States?

　　--No, never. But I went to Canada a few years ago.

A．Have you been

B．Have you gone

C．Did you go

D．Will you go

保护屏必须有接地端子，并用截面不低于（）mm⒉的多股铜线和接地网直接连通。

A.4

B.6

C.10