Ppbv
abbr. parts per billion by volume 十亿分体积比
🗣️ 情景例句
If I fail this exam I'll fail the course.
我要是考试没通过，这门课就没学分了。
Isn't your wife's name Ethel?
尊夫人的名字是不是叫艾雪儿？
About once a month. Not too often, because neither of us has much time. We both have too much work to do.
大约每月一次。不太经常写信，因为我俩的时间都很紧。我们都有做不完的事。