Having在句首,后面加动词的过去分词. 英语中有一种情况,就是现在分词短语做状语,表示时间,原因等,其语法功能相当于一个状语从句.“having +过去分词"位于句首是这种情况的完成时态而已.它强调所发生的动作在主句动作之前.如：Having finished his homework,Tom went home. 像其它时态都有被动语态一样,这种情况也有它的被动语态 having been done 形式：如：Having been told for many times,Tom finally believed it. 使用时应当注意,此类短语的逻辑主语,要与后面主句的主语一致. 如再有疑问,敬请垂询,
