When exactly did the incident occur?

这一事件究竟是什么时候发生的？

《牛津词典》

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When exactly is it?

这具体在什么时候？

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When you hit the nail on the head,exactly on its top, it goes into the wood perfectly.

VOA: special.2009.09.20

Now, when exactly did the American South become a slave society?

那么美国南部究竟是从何时起成为奴隶社会的

耶鲁公开课 - 美国内战与重建课程节选

We'll talk about exactly what a gel is later when we talk about biomechanics and cells are suspended within it.

之后当我们谈到生物力学的时候,会具体讲讲这个凝胶是什么,以及细胞是怎样悬浮在其中的

耶鲁公开课 - 生物医学工程探索课程节选

Where is this so-called hard landing, Mr. Chanos, and when exactly is it supposed to occur?

FORBES: Barclays: China Source Of High Inflation For "Next Decade"

But the agreement is ambiguous about when exactly any reforms may come into force.

ECONOMIST: Another splendid compromise forged in Brussels | The

Experts argue about when exactly the system will begin to pay out more than it takes in.

FORBES: Fact and Comment