引导方式状语从句时as ,as if ,as though有什么区别

as按照.Do as Romans do.入乡随俗.
as if/as though仿佛,好像.A pencil looks as if it were broken when it is partly put in a glass of water.
where引导地点状语从句意思是“在.的地方”.I will go where he studies now.
wherever 表示“任何一个地方,不论何地.”You can go wherever you like.