It will be a long time Mr Black back from abroad.A. before;comesB. since;has comeC. before

问题补充：

It will be a long time Mr Black back from abroad.

A. before;comes

B. since;has come

C. before;will come

D. after;will come

答案：

(答案→)A. before;comes

B. since;has come

C. before;will come

D. after;will come

解析： before 在句中意为“……才……”，后一空考查时间状语从句，用现在时表将来。