Question 4
Mountaineers carry oxygen cylinders with them because :
a) There is no oxygen on high mountains.
b) There is deficiency of oxygen on mountains at high atltitude.
c) oxygen is used for cooking.
d) oxygen keeps them warm at low temperature.
At higher altitudes, the oxygen content decreases which makes breathing difficult for mountaineers. That's why they carry oxygen cylinders. The correct option is b.