The first reason to tackle these problems is to save children's lives.

解决这些问题的首要原因是为了挽救孩子们的生命。

《柯林斯英汉双解大词典》

The first reason is weather change.

第一个原因是天气变化。

youdao

So that's the first reason.

这就是第一个原因。

youdao

Barack Obama said he came to Turkey at the end of his first overseas trip as president for a reason.

VOA: standard.2009.04.06

the first reason that we gave and we are just finishing up is because the question that we ask, whether it's the research questions that we ask, or the questions that we ask of ourselves, or our partners,matter.

我们之前讨论完的第一个原因是,我们提出的问题很重要，无论它是不是我们的研究问题，或我们为自己所问的，或为我们的伴侣问的。

哈佛公开课 - 幸福课课程节选

We will initially think about the first question: Do we have any good reason to believe in souls at all?

我们将要开始考虑第一个问题,我们到底有没有理由去相信灵魂的存在

耶鲁公开课 - 死亡课程节选

The first reason is time: It took about a decade to develop the B-2.

CENTERFORSECURITYPOLICY: Center for Security Policy | SUMMARY OF THE CENTER FOR SECURITY POLICY��S SECOND HIGH-LEVEL ROUNDTABLE ON THE FUTURE OF THE MANNED BOMBER FORCE

So this is the first reason that many ebooks are filled with mistakes and typos.

FORBES: Why Are Ebooks Riddled With Typos?

Mr. QUAMMEN: Well, as far as I'm concerned, the first reason is that it helps us understand cancer better.

NPR: Startling New Evidence Cancer Is Contagious