— I called you at nine this morning, but there was no answer.
— Oh, sorry, I with my sister in the shopping center.
A. shop
B. was shopping
C. shopped
D. will shop
网友回答
A. shop
(答案→)B. was shopping
C. shopped
D. will shop
解析：本题表示过去具体时间所做的事用过去进行时，结构为be+现在分词，故本题选B。