Nitromagnesite
镁硝石
🗣️ 情景例句
We're very lucky, the three of us ...
我们非常幸运， 我们三个……
I know the boy whose father is an engineer.
我知道那个男孩的父亲是工程师。
You must keep it a secret. You mustn't tell anybody else.
你必须保密，谁都不能讲。