英语语法分析

The 40 people with undetectable levels of nicotine and cotinine were classified as nonsmokers;

40位未检出尼古丁和可替宁的志愿者被归类为“非烟民”；

The blood tests check for cotinine- a byproduct of nicotine that usually is detectable for up to four to five days.

验血检查cotinine——一种尼古丁的副产品通常四到五天可被发觉。

They found that there was no level of nicotine or cotinine that did not also correlate with genetic abnormalities.

他们发现零尼古丁或可替宁水平也与基因异常不相关。