— I called you at nine this morning but there was no answer.— Oh sorry I with my siste

问题补充：

— 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

答案：

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。