构成:动词be+v-ing, 动词be加现在分词构成。
经常与现在进行时搭配的时间状语:now, at this time, these days, etc.I was tidying up my room last night. 昨晚我一直在整理房间。When David’s father arrived home, David was playing computer games.当大卫的爸爸回到家时大卫正在玩电脑游戏。 Sally was practising music last night. 萨利昨晚一直练习音乐。