分词做状语和状语从句互换问题
eg: After he had had lunch, he had a cup of tea.这个可以变为: Having had lunch,he had a cup of tea.这个是对的吧, 这种情况的互换有什么说法吗? after 可以,before不可以,有这种说法吗?
eg： Tom had visited his uncle, before he went home. 这种带before 的时间状语从句想变成分词做状语就不和逻辑了啊,求教求教!
补充： 状语从句有时间，原因，条件，让步等等，是不是均适合用分词做状语的形式来改写。 有哪些特例。
如： 由while，when，after引导的时间状语从句都可以用分词做状语来替代，而由before引导的则不成。