as if 后用is 或 was 的疑惑~

looks as if he was dead 和he looks as if he is dead的区别. as if i was It looks as if it is going to rain.后面不该用was going Susan is walking slowly as if she were tired问:为什么用were而不用was the milk smells as if it is sour.为什么不是 as if it was sour啊 The milk smells ___ sour.A.as if it is B.as if it was 一个句子的疑惑...Buildings begin to look less somber,as if they wer ”as+形容词或副词的原级＋as”中后一个as的词性可以是介词吗?我可以说Tom is as tall as （she) "it looked as if it was on fire."的意思? He looks as if he is ill为什么用if 、 有没有as+形容词+as if的表达?如,He was excited as if watching a world-l 虚拟语气中,as if/as though,或even if/even though的用法有哪些?