It looks as if we'll be late. 中的 be 动词

去掉 be 是不对的，但是为什么一定要加上 be，这属于哪条语法规则呢？

回答如下：

As if 引导表语从句，主句用一般现在时态，从句用一般将来时态

主语：It

系动词：looks

引导表语从句连词：as if

从句主语：we

从句谓语：will be

从句表语：late

(备注：we’ll be =we will be ,因为前面有表示将来助动词，后面系动词需要用原形be+作表语的形容词)

以上句子是由as if连词引导表语从句,as if除了引导表语从句还可以引导方式状语从句

(as if 根据放在不同类型动词后可以分为以下2种从句)

【1】如果放在行为动词后则是引导方式状语从句

She loves the boy as if she were his mother．她爱这个男孩好像她是他的妈妈一样.

The child talked to us as if he were a grown-up．这个孩子和我们说话好像是一个成年人.

【2】如果放在系动词后则是引导表语从句

She looks as if she were ten years younger．她看起来好像她年轻了10岁

It seems as if our team is going to win．好像我们队会赢

(as if 引导的从句是否属实可为以下2种从句)

【1】如果表示与事实相符，用陈述语气

She looks as if she is going to cry.她看起来好像要哭了.

【2】如果表示与事实不相符，则用虚拟语气

例如：I remember the whole thing as if it happened yesterday.我记得整个情况好像是昨天发生的一样