Ppm.
[医] 兆比率(百万分之几)
🗣️ 情景例句
Here I am.
我在这儿！
Those that make the best use of their time have none to spare.
能充分利用时间的人不会有时间多馀。
The house was completed five months ago.
是在5个月以前竣工的。