这就是我早早离去的原因。

That's why I left so early.

《牛津词典》

这就是两国纷争的一个原因。

It was a source of disagreement between the two states.

《牛津词典》

我想，这就是我走了几千英里路的原因。

I thought, this is why I've travelled thousands of miles.

《柯林斯英汉双解大词典》

And that's exactly one of the reasons why I want to have the functions, because I've separated those out.

这就是创建方法的原因,只是因为我把，实现和使用分离了。

麻省理工公开课 - 计算机科学及编程导论课程节选

and you say, "ok, this is the reason, and this is the result. This is why I feel the way I feel."

你可以说，“好吧，这就是原因，这就是结果。这就是我有这种感觉的原因。”

That's why 课堂 - SpeakingMax英语口语达人

We're exposed to things that might cause cancer where weren't exposed to them before and so that might be a reason.

我们暴露于可能致癌的物质中,这些物质在以前是没有的,这可能就是原因之一

耶鲁公开课 - 生物医学工程探索课程节选