1 It seems that she knows our city well(用于主语从句,做谓语)==She seems to know our city well（用于简单句,做复合谓语）
2 She looks / looked as if she had seen a ghost.（用于虚拟语气）
3 She looks as if she has been working very hard for a long time===She seems to have been working hard for a long time (用于非虚拟语气,似乎,好像)
--------look as if + 句子：
------ look as if + 表语从句