Underwater, divers must breathe a combination

The correct answer that would best complete the given statement above would be OXYGEN and HELIUM. Or in other terms, it is known as HELIOX. Heliox is the mixture of oxygen and helium and it has a lesser density than air. Using heliox for breathing decreases the resistance to flow within the airways and also decreases the work of breathing. Hope this answer helps.

I hope this helps
M=30g