Doctors do not yet know why this is true.

VOA: special.2010.06.15

I have a way to account for that, but it's going to take to the end of my argument to do that, so I'm going to argue that that's significant, but I'm not going to talk about why it's significant yet.

我对那有自己的理解，但是我在最后才会告诉你们，我要跟你们说，那点的意义是非常重大的，但我现在还不能谈论它的重大意义。

耶鲁公开课 - 1945年后的美国小说课程节选

That is one of the major points as to why deafness has not gotten a cure yet.

这就是到目前为止,还没有对策的一个主要原因。

斯坦福公开课 - 7个颠覆你思想的演讲课程节选