as if/though+主语+过去时/过去完成时/would/could/might+do
Eg：①表语从句：The girl is giving us a vivid description of the moon it seems as if she had been to the moon many times.(事实上并未去过)
这个女孩对月球所做的逼真的描述就好像她去过月球多次似的.
②状语从句：The young man with long hair walks as if he were/was a girl.（他不是小姑娘）
留长发的那个小伙子走起路来就像个小姑娘.
与过去事实相反用一般过去时,与过去事实相反用过去完成时,与将来事实相反用would/could/might+do