问题
选择题
What ________ you ________ at this time yesterday?
A．did, do
B．have, done
C．were, doing
D．are, doing
答案
答案：C
题目分析：at this time yesterday,昨天的这个时间，过去进行时的标志。过去进行时的结构：was / were +V-ing .结合句意，昨天这个时候你正在干什么？故选C。