在主从句中充当表语成分例句，who

Who可以引导表语从句，但它的意思应该是表示“谁”。

如：

The problem is who is to blame.

The problem is who is to pay and when we can start.

Destiny has ordained that they are who they are. 命运已经决定了他们的性格和为人。

who 的三种用法：

1、 疑问代词，引导特殊疑问句：Who are you talking about?

2、 连接代词，引导名词性从句：

如：I don’t know who you are talking about.

3、 复合关系代词（也可叫复合连接代词），引导名词性从句：

如：The woman is very rich now. She isn’t who she was. 这位女子现在很有钱了，她不是以前的那个她了。

When you come back，you will know who is the better one.你回来了才会知道谁才是更好的那个。