有读者问这样一个句子：
(1)He heard a noise as if someone was breathing.
《现代英语语法手册》上说“由 as if 所引导的状语从句表示比较或方式时，从句的谓语动词用虚拟语气。动词形式用过去式 (be 用 were)或 had+过去分词”。但上述引文却用 was 而不用 were, 这是为什么？
《现代英语语法手册》讲得没有错，许多语法书都这样说。但它们皆指规范英语而言。在不很规范或不很正式的英语里，as if 之后则常用过去虚拟式 was 代替 were, 再如：
(2)All this was over twenty years ago, but it's as if it was only yesterday.
(3)All shook their hands and were very grave; for it seemed as if there was no hope.
这里有必要指出， as if 从句如有真实性，即如表一事实，则可用普通时态，如：
(4)He acts as if he is in love with her.
(5)She looks as if she will be like you when she grows up.
这样说来，下面一句，孤立地看，就有歧义了:
(6)She treated me as if I was a stranger.
这里的 was 可能是一虚拟时态（无真实性），也可能是一普通时态（有真实性）。
这样说来，孤立地看，上述句（1）与句（3）也都会有歧义了。当然，在一定的上下文中，上述例句大都是不会有歧义的。
