Hi Bob. How are you doing? It has been a long time we left our junior middle school.A. w

问题补充：

Hi, Bob. How are you doing? It has been a long time we left our junior middle school.

A. when

B. that

C. before

D. since

答案：

A. when

B. that

C. before

(答案→)D. since

解析：此处主句是现在完成时，从句是一般过去时，所以选since。句意：Bob你过得怎么样？自从我们初中毕业很长时间了。