Radioactive background
[化] 放射性本底
🧩 词语组成解析
🗣️ 情景例句
When he came to the States five years ago, he had only forty dollars in his pocket.
五年前他来美国时，口袋里只有40美元。
I think we may be able to work together in the future.
我想也许将来我们可以合作。
Bye.
再见。