.We were just about ready to leave it started to rain. A. whenB. beforeC. afterD. since

问题补充：

.We were just about ready to leave it started to rain.

A. when

B. before

C. after

D. since

答案：

(答案→)A. when

B. before

C. after

D. since

解析：连词辨析。A. 当……时 B. 在……之前 C. 在……之后 D. 自从……以来，句意：当开始下雨时，我们正准备离开。故选A。