复数： chemicals

Bacteria communicate with their neighbours through chemical signals .

细菌通过化学信号与周围的细菌进行联系。

Many chemical producers have been asked to cooperate .

许多化学品生产商已经被要求提供合作。

Chemical use in american agriculture peaked soon thereafter , in 1973 .

就在此后不久的1973年，化学药品在美国农业中的使用达到了顶峰。

And as more people participate , both the chemical trail and the overall system grow stronger .

当更多人开始参与，这种化学的信号和整体的系统将越来越强大。

The chemical can make meat leaner , but can also be the cause of heart palpitations , diarrhoea and muscle tremors .

这个化学剂可以减少肉的脂肪，但同时也可能引起心跳加速、腹泻以及肌肉颤抖。