Ppb
[化] 十亿分率
🗣️ 情景例句
These are polite questions.
这些问题都是礼貌的。
Put the cart before the horse.
本末倒置。
Paw prints were seen in a number of places and puma fur was found clinging to bushes.
在许多地方看见爪印，灌木丛中发现了粘在上面的美洲狮毛。