如 At 7 o"clock YESTERDAY evening i heard him _____ (唱歌) in the next room 此题答案为什么是

问题描述:

如 At 7 o"clock YESTERDAY evening i heard him _____ (唱歌) in the next room 此题答案为什么是
singing 如果是过去进行时的话那不应该是 was singing

hear sb doing 固定用法,听到某人正在做某事,就不用加was了~