sth happened when sb was doing sth sth happened while sb was doing sth 有没有sb was doing sth when sth happened 我在考卷上看到一个填空的sb ---- down the street when sth happened 用walk的形式填空 怎么办
sb was doing sth when sth happened 和 sth happened while sb was doing sth都有,“当某事发生时,某人正在做某事”,而由于when表时间“点”while表时间“段”,故很少用sth happened when sb was doing sth。但when还有另外的结构:sb did sth when sth happened(强调...