Having been told that some guests were coming, she sTOPped all morningin that supermarket.
这句话中为何是用having been told?
when asked the reason for their success，the kids had twoexplanation.
这两句话非常像，但第二句就用的是asked，同样都是主句为过去，从句要用被动态过去分词，为何第二句不需要having been asked呢？
第一句sTOPped 应为 shopped.
第一句作状语的having beentold为目前分词完成体被动语态。之所以用完成体，是由于告诉的动作发生在谓语动作之前。第二句是when引导时间状语从句，省略了主语和be, when asked = when the kids were asked. When引导时间状语从句，可以表示主句的动作紧接着从句的动作发生。比如，When he opened the door, he saw Tom. 这个when从句是没必要用过去完成时的，由于从句和主句的动词衔接发生。假如二个动作之间有较长的时间间隔，则从句就需要用完成体。比如，When he had sold his old house, he moved to Shanghai.