—I called you at 4:00 yesterday afternoon but no one answered.—Sorry I with my friends

问题补充：

—I called you at 4:00 yesterday afternoon, but no one answered.

—Sorry, I with my friends at that time.

A. swim

B. swam

C. will swim

D. was swimming

答案：

A. swim

B. swam

C. will swim

(答案→)D. was swimming

解析： 考查时态。根据时间状语yesterday afternoon,可知要用过去时态；再据at that time，可知要用过去进行时态。所以选D。