I know what you're talking about. 我知道你在說(shuō)什么。
This is exactly what I'm talking about. 這就是我想說(shuō)的。
You know who I'm talking about. 你知道我說(shuō)的是誰(shuí)。
I have no idea what you're talking about. 我搞不清你說(shuō)的東西。
I saw you out with another woman. 我看見你和一個(gè)女人出去了。
I don't know what you're talking about. 我不知道你在說(shuō)什么。