These changes weren't happening in a vacuum.

些改变并不是凭空出。

But there are different accounts about how this happened.

但对于次事件如何发生也有不同言论。

Human flow has always happens in human history.

人口流动是人类历史上经常发生事。

And that doesn't happen by cramming.

但是死记硬背并不能实过程。

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

哦，不不不。可糟了。

And there are many points where their failure happens.

失败因素出在各个环节。

The building was being demolished when the collapse happened.

座大楼在拆除过程。

To put it simply, everything happens instantaneously.

简单来说切都会在瞬间完成。

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

所有切都可能发生在任何人身上，也确实发生在每个人身上。

It suggests that the work is happening.

表明工作正在进行。

Without it, the competition could not happen.

如果它们没有招，个比赛也没啥比。

So, why is it happening at all?

那么，到底为什么发生呢？

Those changes didn't happen on their own.

些改变不是自动发生。

Okay. There has been a lot happening.

好。发生了很多事。

But what if it happens too often?

但如果种情况发生得太频繁了呢？

Scientists are still unsure why this happens.

科学家仍不确定为什么会样。

I think that this happens since March.

我认为是从 3 月份开始。

How old was she when this happened?

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，类交易就开始了。