Which of the following gases is mixed with oxygen for breathing by divers in aqua lungs?

Answer: Option C

Divers need to breathe underwater, right? But they can't just breathe regular air from the surface. The air we breathe is mostly nitrogen and oxygen.

At great depths, nitrogen can have some bad effects on the body. That's why divers use a special mix of gases.

This special mix often includes oxygen, of course, because we need oxygen to live. But instead of using all nitrogen, they mix in another gas that is safer at depth.

Helium is a much safer choice because it doesn't cause the same problems as nitrogen at high pressures.

So, the answer isn't methane, nitrogen, or hydrogen. The right answer is helium because it's used with oxygen in scuba tanks to allow divers to breathe safely at depth.