According to the occurrence of yellow insects of covered crisp pear in Shanxi, this paper discusses the reasons why it occurs and provides integrated cure measures for yellow insects pests.

针对山西省酥梨黄粉虫的发生情况，论述了套装酥梨黄粉虫发生的原因，提出了黄粉虫的综合治理措施。

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We don't know exactly why the pain occurs, but it can be very debilitating — to the point that patients decide to stop taking aromatase inhibitors.

我们不知道疼痛发生的准确原因，但是这种疼痛使人变得很虚弱，以至于患者会决定停止服用芳香化酶抑制剂。

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In other words, an event consumer doesn't care where or why an event occurs; rather, it's concerned that it will be invoked when the event has occurred.

也就是说，事件消费者不关心事件发生的地点或原因；而是关注事件发生后它（消费者）将被调用。

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That's why it's natural to point to the moment of star when we say that's when my death occurs.

所以很自然的，我就死在星号这里。

耶鲁公开课 - 死亡课程节选

But for now let's simply say that we have a diffraction which we know occurs only by wave-like behavior and it involves the use of x-rays. Why x-rays?

但现在让我们来简单假设一下,我们知道,只波才发生衍射,而且衍射涉及了X光的使用，为什么是X光？

麻省理工公开课 - 固态化学导论课程节选

The fact that we are in 2012, and have recognized the problem of statins engendering diabetes for the past 4-5 years, have no clue for why it occurs, and that nothing has been done about it in the medical community or by the life science industry, is truly remarkable.

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It is why the BCS championship occurs on Monday prime time in early January, not the calm of New Year's Day.

WSJ: The Money Train That Is Sports TV

To understand why, it has to be remembered that since trade tautologically occurs among individuals, it always balances among individuals.

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