When I dropped in Dr Smith so we only had time for a few words.A. just leftB. was just

问题补充：

When I dropped in, Dr Smith , so we only had time for a few words.

A. just left

B. was just leaving

C. has just left

D. had just left

答案：

A. just left

(答案→)B. was just leaving

C. has just left

D. had just left

解析：此题重点考查过去进行时的基本用法，表示过去某一时间正在进行的动作或存在的某种状态。