Mrs White walked into the house,followed by her children.

还原成简单句：等于Mrs White walked into the house,（and she was ）followed by her children。伴随状语,动作是由children发出,可以理解为Mrs White是被动的。如果是Mrs White发出,就是ing形式。这只是理解的一种方法。这种题目高中很多。多问问老师,归类很重要。