Question

They ________ friends since they met in Shanghai．

[　　]

A．

have made

B．

have become

C．

have been

D．

have turned

Answer 1

答案：C
解析：

当从句中使用since来引导时，表示“自从……以来”，主句要用现在完成时，而且此时主句的谓语动词必须是延续性的。