- Have you known each other for long?- Not reallywe started to work in this school.A. J

问题补充：

- Have you known each other for long?

- Not really. we started to work in this school.

A. Just after

B. Just when

C. Ever since

D. Just before

答案：

A. Just after

B. Just when

(答案→)C. Ever since

D. Just before

解析：考查连词：A. Just after就在…后面，B. Just when就在…时候，C. Ever since自从，D. Just before就在…前面，句意：--你们认得彼此很长时间了吗？--不是，（我们认得）是自从在这个学校学习以来。这句话的主句We have known each other被省略了，所以从句用ever since（和现在完成时连用），选C。