--I called you at 4:00 yesterday afternoon but nobody answered. ----Sorry Iwith my fri

问题补充：

----I called you at 4:00 yesterday afternoon ,but nobody answered.

----Sorry,Iwith 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：句意：昨天下午我给你打电话了，但是没人接。很抱歉，那时我正在和朋友游泳。at that time是过去进行时的标志词，结合句意，故选D.