问题补充：
Unluckily, when I dropped in , Dr. Smith , so we only had time for a few words.
A. was just leaving
B. has just left
C. had just left
D. just left
答案：
(答案→)A. was just leaving
B. has just left
C. had just left
D. just left
解析：由so we only had time for a few words可知：当我们到访时，Dr. Smith. 正要离开，was leaving过去进行时表将来。故选A。
