— I phoned you at 7 yesterday evening but nobody answered.— Oh I my dog in the park then.

问题补充：

— I phoned you at 7 yesterday evening but nobody answered.

— Oh, I my dog in the park then.

A. walked

B. was walking

C. had walked

D. would walk

答案：

A. walked

(答案→)B. was walking

C. had walked

D. would walk

解析：考查时态：句意：--昨天晚上7点我打电话给你，但是没有人接电话。--哦，那个时候我正在公园遛狗。这里的then指的是at 7 yesterday evening，所以遛狗这个动作是过去某个时间正在做，用过去进行时。选B。