I was almost asleep last night when I suddenly heard someone at the door.A. be knockingB.

发布时间：2020-08-17 12:13:05

I was almost asleep last night when I suddenly heard someone      at the door.
A. be knocking
B. knocking
C. to knock
D. having knocked

网友回答

A. be knocking
(答案→)B. knocking
C. to knock
D. having knocked
解析：  本题考查对动词习惯用法的掌握。 hear sb. doing sth．意为听见某人正在做某事。
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