Question

Deep sea swimmers and astronauts carry oxygen cylinders with them.where else are oxygen cylinders used?

Answer 1

They use oxygen cylinders because in the deep seas,and astronauts will carry oxygen cylinders are not available or possible oxygen to breathe.in the  sea we will go down means the oxygen level will decreases .like that only above the troposphere also the oxygen levels will decreases.the oxygen level will decreases and the temperature will increase