as if 用法歸納：

　　as if一般可由as though來代替。可在look, seem等系動詞后引導(dǎo)表語從句。如:

　　It seems as if it is going to rain.

　　看來好像要下雨了。

　　as if 從句的語氣及時態(tài)

　　當(dāng)說話者認(rèn)為句子所述的是真實的或極有可能發(fā)生或存在的事實時,as if從句用陳述語氣。如:

　　It sounds as if it is raining.

　　聽起來像在下雨。