9.Unfortunately,when i dropped in ,proffesor smith( ),so we only had time for a few words.

9.Unfortunately,when i dropped in ,proffesor smith( ),so we only had time for a few words.
A.has just left B.has just left
C.just left D.was just leaving
Q:have 时间发生在什么动作之前,是leave之前吗?用过去完成事态had+done,其参照点(过去的那个动作)不一定就用一般过去时态,还可以用哪些时态喃?最好有例句说明,thank you
D 写掉了 我主要想问 为什么题中是so we only had time for a few words,里要用过去完成时态.