问题补充：
What at nine o’clock last Sunday morning.?
A. was you doing
B. were you doing
C. are they doing
D. do you do
答案：
A. was you doing
(答案→)B. were you doing
C. are they doing
D. do you do
解析：此题重点考查过去进行时的特殊疑问句的基本构成。表示过去具体时间所做的事用过去进行时，结构为was或were doing，第二人称you用were，故本题选B。
