Ppm.
[医] 兆比率(百万分之几)
🗣️ 情景例句
Would you kindly hold these keys, please?
请帮我拿一下钥匙。
Let me lend it to you.
让我借给你。
is the slowest and has travelled round the earth through the surface rocks.
是最慢的，是围绕地球通过表面岩石传来的。