Ppbv
abbr. parts per billion by volume 十亿分体积比
🗣️ 情景例句
I'm awfully sorry.
非常抱歉。
What were you doing at about 4 o'clock yesterday afternoon?
你昨天下午在大约4点钟正在做什么？
He became a supporter of the poorest group in society, who did the lowest-paid jobs.
他成为社会中那些从事工资最低的工作的，最穷种姓的支持者。