Give reasons why:

(a) This is bacuse at high altitudes, the atmospheric pressure because of the gases present above is low. Hence, volume is more. So, the density of oxygen becaomes less. Hence, mountaineers carry oxygen cylinder with them.

(b) -273 degree celsius is equal to 0K which is the minimum possible temperature since below this temeprature nothing can exist.

(c) Air at sea level is dense because atomispheric pressure is highest at sea level. Hence, volume is low.