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:考查固定句型。固定句型:be doing sth when…正在做某事在这时…when后面的句子指发生了意料之外的事情。When是一个并列连词,意为“在这时”。句意:我们正在湖里游泳,在这时突然下起了大暴雨。故A正确。