Question

why the mountaineers climbing Mount Everest take oxygen cylinders with them

Answer 1

As we know that when we go higher an higher the layer of atmosphere goes thinner.It becomes difficult to breath.

After going at a great height the amount of oxygen also decreases. Therefore to survive we need to take oxygen cylinders while climbing mountains like Mt.Everest

One more example is in Space when Astronauts go in space the layer of atmosphere goes thinner and oxygen is not available in Space .

Answer 2

because when we go more and more high in the sky then there is loss of oxygen.