And as I will explain in a second there are many reasons why this sense hasn't really been elucidated at the molecular level.

难以真正从分子学的角度阐明,这种感官的原因是多方面的,有关这一点,稍后我会另行解释。

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So there are various reasons why it's hard to maintain this collusive agreement.

这样的私下协议难以维系,是有多方面原因的

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