A: a reversal in the rotation of Earth is impossible.

答：地球发生相反方向的旋转是不可能的。

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By the principle of reversal process, the formula of material removal rate (MRR) in wafer rotation grinding process is deduced. The relationship between MRR and the grinding parameters is given.

在反转法的原理上，建立了硅片自旋转磨削材料去除率的理论模型，推导了材料去除率公式，分析了磨削工艺参数与材料去除率的关系。

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They clfunction a relationship within the rotation and the magnetic polarity of Earth, which does change irregularly, with a magnetic reversal taking place every 400,000 years on audio-videoerage.

他们声称地球磁极和自转有相关。地球的磁极的确会不规律的改变， 大约均匀400，000年发生一次磁极转换。

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