As part of the formula, they measured a biological marker, total NNAL, which indicates the amount of exposure to the tobacco-specific lung cancer-causing agent NNK.

作为公式的一部分，他们测定了生物标记物——总nnal含量，它能够反应烟草特异致肺癌成分nnk的含量。

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There are many forms of expression of passive sentences in Japanese, which is mainly displayed in various forms of the marker of the agent.

日语被动句有多种表现形式，其核心就是动作主体表现的不同。

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