Ppm.
[医] 兆比率(百万分之几)
🗣️ 情景例句
all about your first full day back on the job.
关于你重回工作第一天的全部情况了。
Would you care for a cop of coffee?
要被咖啡吗？
Once the oxygen content of the air had risen to 25% it was ready to burn.
一旦氧气在空气中的含量达到25%，它就要燃烧。