Ppb
[化] 十亿分率
🗣️ 情景例句
It was dumb of you to say that.
你说那种话真的是太愚蠢了。
I never used to oversleep.
我过去从未睡过头。
It was his job to repair bicycles and at that time he used to work fourteen hours a day.
他那时的工作是修理自行车，并且通常是一天工作14个小时。