What at nine o’clock last Sunday morning?A. was you doingB. were you doingC. are they doin

问题补充：

What at nine o’clock last Sunday morning?

A. was you doingB. were you doingC. are they doing

答案：

解析：此题重点考查过去进行时的基本用法，表示在过去某个时刻正在进行的动作或存在的某种状态。根据语境可知此句的含义上周日的早晨9点中你正在干什么。故用过去进行时。过去进行时的基本构成是was或were+ving，故选B。