Question

___________ is a life-supporting gas as it is necessary for respiration.

Answer 1

• The process in which food combines with Oxygen to form Carbon dioxide, water vapour and energy is called respiration.
• $\mathrm{Food}+\mathrm{Oxygen}\to \mathrm{Carbon}\mathrm{dioxide}+\mathrm{Water}\mathrm{vapor}+\mathrm{Energy}$

Hence, Oxygen is a life-supporting gas as it is necessary for respiration.