我们有确凿无疑的证据证明到底发生了什么。

We have incontrovertible evidence of what took place.

《柯林斯英汉双解大词典》

我说不准到底发生了什么事。

I can't rightly say what happened.

《牛津词典》

警方正设法查清到底发生了什么。

The police are trying to ascertain what really happened.

《牛津词典》

So, let me go had and let's swivel this around for just a moment so we have a blank slate and now what's really going on?

我把它旋转一下,这样就有一块空白了,到底发生了什么呢？

哈佛公开课 - 计算机科学课程节选

There may be some inefficiencies, and at some point, if you catch me in the hallway, I can give you a sermon on what goes on inside that reactor.

可能会有某些损耗，如果你能在过道上遇到我的话，我会给你详细讲讲,里面到底发生了什么。

麻省理工公开课 - 固态化学导论课程节选

Let's see what happens here, just the motif, one, two, three, four, three four, one two, and then the theme.

让我们看看到底发生了什么,正是动机,一,二,三,四,一遍又一遍,然后是主题

耶鲁公开课 - 聆听音乐课程节选