英语（现在完成时）,leave的用法

我们说的瞬间动词不能用在现在完成时中,是指当句子中有表示时间段的状语的时候不能用,而一般情况下是可以用的。比如说I have joined the army for three years就是错的,join是个瞬间动词,当加上一段时间的时候需要作相应的变化,也就是I have been a member in the army for three years。I have left my book at home是个正确的句子,因为这句话没有表示时间段的状语。还有I have left school是正确的,如果要加上时间状语for three days就要变成I have been away from school for three days。I have left my book at home如果要加上时间状语的话可以改为I have kept my book at home for three hours。