29 ___ (catch) the last bus,he had to go home by taxi.为什么用NOT having caught 不用Not have caught.
问题描述：
29 ___ (catch) the last bus,he had to go home by taxi.为什么用NOT having caught 不用Not have caught.
答
原因状语从句 只有ing form 才可以充当
答
此处have caught....不是谓语，而是状语。
对于初学者，弄清楚动词是否作谓语，再决定其动词形式很重要！
答
not having caught 是现在分词的完成式,作原因状语，表示其动作发生在位于动词之前。相当于Since he hadn't caught the last bus, he had to go home by taxi.
答
Hadn't caught
答
NOT having caught 是完成时的分词形式.
NOT having caught the last bus是从句所以不能独自成句,也就不能用Not have caught,只能用他的分词形式NOT having caught .
答
时态
过去进行时的嘛
那个时间没赶上公交车，过去在进行的，
他必须坐出租车，过去发生的。