In the given figure, a burning candle is kept in the trough containing water. It is put off after some time when covered by an inverted gas jar. What can be concluded from the above activity?

• A.  Oxygen is 1/5th the volume of air.
• B.      The ratio of oxygen and nitrogen in air is 1 : 4.
• C.      Oxygen is required for burning the candle.
• D.      All of the above