－Have you known each other for long?－Not very long we started to work in the company.A.

问题补充：

－Have you known each other for long?

－Not very long, we started to work in the company.

A. after

B. before

C. when

D. since

答案：

A. after

B. before

C. when

(答案→)D. since

解析：句意：--你们认识很长时间了吗？--不很长，自从我们在一个公司上班。After在……之后； before在……之前； when当……时候； since自从。因为答语是省略句，

完整的是：We haven known each other since we started to work in the company.只有since表示从过去到现在一直认识，并且它与现在完成时连用，故选D。