Tephra
[复]n.[用作单或复][地]火山灰
🗣️ 情景例句
Do you have a picture?
你们有他的照片吗？
Same to you!
也祝你快乐！
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。