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。