It is a matter of the utmost urgency to find out what has happened to these people.

当务之急是弄清楚这些人出了什么事。

《柯林斯英汉双解大词典》

We are bitterly upset at what has happened.

我们对发生的事感到极其难过。

《柯林斯英汉双解大词典》

It is time to bury the hatchet and forget about what has happened in the past.

是言归于好并忘记过去发生的事的时候了。

《柯林斯英汉双解大词典》

He says this is a very huge increase compared to what has happened in the past.

VOA: special.2009.06.03

A lot has happened since the exuberant optimism of the political spirit that we see in a tract like Areopagitica.

弥尔顿在《论出版自由》中发表了极为乐观的政治思想之后,政治形势发生了很大变化。

耶鲁公开课 - 弥尔顿课程节选

or if you're feeling like a big event has happened. Or if you're feeling that they look really great.

或者你觉得对方发生了什么大事，或者是你觉得他们看起来棒极了。

You look 课堂 - SpeakingMax英语口语达人

Certainly that is what the data suggests has happened over the last several decades.

FORBES: NFL And Wisconsin Polls Showing Support for Players And Governor Walker

It works but what has happened is that Apple have changed the way websites are approved.

FORBES: First There Was Apple's MapGate, Now Welcome ParentGate

It will take a long time for his family to get over what has happened here.

BBC: Chick Young's view