The key question of what caused the leak remains unanswered.

泄漏究竟是怎么造成的，这一关键问题仍未得到答案。

《牛津词典》

At the heart of the debate over illegal immigration lies one key question: are immigrants good or bad for the economy?

关于非法移民的争论的核心是一个关键问题：移民对经济是好还是坏？

youdao

But he added that the overall research in this area is "still in its infancy" and one key question is whether literary fiction really is better than other fiction.

但他补充说，该领域的整体研究“仍处于起步阶段”，一个关键问题是，文学小说是否真的比其他小说更好。

youdao

Analysts say a key question is whether Russia will continue to insist missile defense be linked to the conclusion of an arms-control agreement.

VOA: standard.2009.07.15

Should we conclude,therefore, that the key to the important question--namely, What matters? the answer to that question, should we conclude,is,same personality?

我们是否就该得出结论，重要问题的关键，也就是什么是最重要的，这问题的答案就是相同的人格吗？

耶鲁公开课 - 死亡课程节选

But the lawmakers, both members of the Senate Intelligence Committee, were directly at odds over another key question -- whether Clarke's latest statements contradict testimony he gave a congressional panel investigating the attacks two years ago.

CNN: Rice may testify before 9/11 panel by next week

The key - and legitimate - question now is not about the defence secretary's private life but what Adam Werritty's role was and how he paid or was paid for following Liam Fox around the world.

BBC: Liam Fox claims to be hate campaign victim

The findings of the study, which examined the subjects during just one 50-minute exposure, raise a key question, the researchers said: What, if any, are the long-term consequences of repeated increased brain activity due to exposure to cell phone radiation?

CNN: Cell phone exposure increases brain cell activity