对现在的虚拟 过去：It looked as if they had been good friends 将来：It looked as if they would be good friends

以as if (as though)引导的方式状语从句或表语从句，有时用虚拟语气。 当说话者认为句子所述的是真实的或极有可能发生或存在的事实时。 如： It sounds as if it is raining． 听起来像是在下雨。 He talks as if he is drunk． 从他谈话的样子来看他是醉了。 as if 从句用虚拟语气的情况是当说话人认为句子所述的是不真实的或极少有可能发生或 存在的情况时。从句虚拟语气动词时态的形式如下： （1）如果从句表示与现在事实相反，谓语动词用一般过去时 如： You look as if you didn” t care． 你看上去好像并不在乎。 He talks as if he knew where she was． 他说话的样子，好像他知道她在哪里似的。 （2）从句表示与过去事实相反，谓语动词用“had＋过去分词”。 如： He talks about Rome as if he had been there before． 他说起罗马来好像他以前去过罗马似的。 The girl listened as if she had been turned to stone． 那女孩倾听着，一动也不动，像已经变成了石头似的。 （3）从句表示与将来事实相反，谓语动词用“would／could／might＋动词原形”。 如： He opened his mouth as if he would say something． 他张开嘴好像要说什么。 It looks as if it might snow． 看来好像要下雪了。 引用 ： http://blog.sina.com.cn/s/blog_6d4b41780100nn8r.html 从上面可以看出，It looked as if they were good friends。是对一般现在时的虚拟，表示与事实相反。（在外人看来）他们就好像是好朋友，（其实。。。。）。有引申义的。

在这句话 动词形式看上去像过去的，非真实的，虚拟语气。 Why do we say "I were", "he were"? We sometimes hear things like "if I were you, I would go" or "if he were here, he would tell you". Normally, the past tense of the verb "to be" is: I was, he was. But the if I were you structure does not use the past simple tense of the verb "to be". It uses the past subjunctive of the verb "to be". In the following examples, you can see that we often use the subjunctive form were instead of "was" after: •if •as if •wish •suppose Formal (The were form is correct at all times.) If I were younger, I would go. If he weren't so mean, he would buy one for me. I wish I weren't so slow! I wish it were longer. It's not as if I were ugly. She acts as if she were Queen. If I were you, I should tell her. Informal (The was form is possible in informal, familiar conversation.) If I was younger, I would go. If he wasn't so mean, he would buy one for me. I wish I wasn't so slow! I wish it was longer. It's not as if I was ugly. She acts as if she was Queen. Note: We do not normally say "if I was you", even in familiar conversation.