How will you prove that air supports burning?

A candle burns in the presence of air. To prove this, we will take two candles of same length and burn them. After some time, we will use an inverted glass jar to cover one of the candles and the other one will be left as it is. After a few seconds, we will observe that the candle covered with the glass jar has extinguished but the one on without the glass jar has not.

And the reason behind this is that air has oxygen in it which is a gas that supports burning. When we covered the candle with the inverted glass jar, we cut off the air supply for that candle. Since the air left in the jar is used up in a few seconds, the flame of that candle extinguishes. Where as the candle left as it was, there is plenty of air for it to continue burning. 

Hence, we can say that air supports burning.