These changes weren't happening in a vacuum.

这些改变并是凭空出现。

But there are different accounts about how this happened.

但对于这次事件如何发生有言论。

Human flow has always happens in human history.

人口流动是人类历史经常发生事。

And that doesn't happen by cramming.

但是死记硬背并能实现这一过程。

Oh, no, no, no. What a thing to happen.

哦，。这可糟了。

And there are many points where their failure happens.

失败因素出现在各个环节。

The building was being demolished when the collapse happened.

这座大楼在拆除过程中倒塌。

To put it simply, everything happens instantaneously.

简单来说一切都会在瞬间完成。

All these things can happen to anyone, and they happen to everyone.

所有这一切都可能发生在任何人，确实发生在每一个人。

It suggests that the work is happening.

这表明工作正在进行。

Without it, the competition could not happen.

如果它们没有这招，这个比赛没啥比。

So, why is it happening at all?

那么，这到底为什么发生呢？

Those changes didn't happen on their own.

这些改变是自动发生。

Okay. There has been a lot happening.

好。发生了很多事。

But what if it happens too often?

但如果这种情况发生得太频繁了呢？

Scientists are still unsure why this happens.

科学家仍确定为什么会这样。

I think that this happens since March.

我认为这是从 3 月份开始。

How old was she when this happened?

这件事发生时候她多大？

Every time something happens, something else happens.

每次有某事发生，就会有别事情发生。

That's thought to have happened after breakup of the Soviet Union.

据了解，自从苏联解体之后，这类交易就开始了。