• Brainly User
It is because you need to gather more oxygen and accommodate in yourself as there are some breathing problems high atop a mountain as higher the atmospheric pressure the thinner the air.
5 2 5
As we know that as the altitude increases, the atmospheric pressure decreases. Due to thinner air, less amount of oxygen is available. And this is why we need to breath faster because in one breath, sufficient amount of oxygen is not available. 
10 4 10
i think should take physics tutions from u
and i think i should take bio tutions from u
u r always welcome