第三种是某些基本的化学物质，如碳、氧和氮。

A third is certain basic chemicals such as carbon, oxygen and nitrogen.

youdao

还有第三种脑化学物质也是不可或缺的。

And there's a third brain chemical that comes into play.

youdao

还有第三种脑化学物质也是不可或缺的。

And there's a third brain chemical that comes into play.

youdao