过去进行时 (Past continuous)

小测验

1. They ______ playing cards when the lights went out.

   was · were · are

   显示答案

   were — 主语 they 用 were + playing。

2. I was reading when someone ______ at the door.

   was knocking · knocks · knocked

   显示答案

   knocked — 突然发生的短动作用一般过去时 knocked。

3. What ______ you doing at ten last night?

   were · was · did

   显示答案

   were — 过去某一时刻正在做什么：were you doing。