We were swimming in the lake suddenly the storm started.A. whenB. whileC. untilD. before

问题补充：

We were swimming in the lake suddenly the storm started.

A. when

B. while

C. until

D. before

答案：

(答案→)A. when

B. while

C. until

D. before

解析：句意：我们正在湖里游泳这时突然暴风来了。Be doing when…正在做某事突然；while当……时候；until在以前；before在……以前。根据句意故选A。