We ____ for tom at ten last Sunday.He often kept us ______.a.were waiting,waiting b.were waiting,wait c.waited,waiting d.waited,wait 加以说明

We ____ for tom at ten last Sunday.He often kept us ______.a.were waiting,waiting b.were waiting,wait c.waited,waiting d.waited,wait 加以说明
We ____ for tom at ten last Sunday.He often kept us ______.a.were waiting,waiting b.were waiting,wait c.waited,waiting d.waited,wait 加以说明

We ____ for tom at ten last Sunday.He often kept us ______.a.were waiting,waiting b.were waiting,wait c.waited,waiting d.waited,wait 加以说明
A
were waiting 是指当时正在进行等待
keep sb.doing sth.是固定句型,ing形式表示正在发生,或过去一段时间一直发生的动作,这个动作直到Tom来到才停止,所以可以理解为是Tom使我们保持（等待）这个动作,这个动作一直在发生,所以用ing形式,而不是原形