上课了，许老师笑容满面地对我们说:你们想做小实验吗!同学们兴致勃勃说道:想!
In class, Mr. Xu said to us with a smile: do you want to do a small experiment? The students said excitedly: Yes!
只见许老师从一个纸盒里拿出透明的杯子，一根红红的蜡烛和一个打火机啪一声打着了火，点燃了蜡烛。神秘地说:请同学们细心观察我们都想很好奇，想看看究竟。这时老师慢慢地把杯子往下移，火苗渐渐变小了，最后无力的颤抖了一下，火灭了冒出了烟。老师问:火苗为什么灭呢我们纷纷举手，老师请我回答，我胸有成竹地说:因为燃烧需要空气。
Xu took out the transparent cup from a cardboard box. A red candle and a lighter started the fire and lit the candle. Mysteriously said: please observe carefully we all want to be curious, want to see exactly. At this time, the teacher slowly moved the cup down, and the fire gradually became smaller. Finally, the teacher shivered weakly, and the fire went out and gave out smoke. Teacher asked: Why did the fire go out? We raised our hands one after another. The teacher asked me to answer. I said with confidence: because combustion needs air.
同学们，你们知道吗燃烧需要空气。
Students, do you know that burning requires air.