The inert gas which is substituted for nitrogen in the air used by deep sea divers for breathing is: A. Neon B. Argon C. Krypton D. Helium

The correct answer is D. Helium.

Helium is the most abundant element in the universe, but it is only a very small fraction of the air we breathe. It is a colorless, odorless, and tasteless gas that is

lighter than air. Helium is used in deep sea diving because it is less soluble in blood than nitrogen. This means that divers can breathe helium-oxygen mixtures without the risk of nitrogen narcosis, a condition that can cause confusion, impaired judgment, and even death.

Neon, argon, and krypton are also inert gases, but they are not used in deep sea diving because they are

more soluble in blood than helium. This means that divers who breathe these gases are at risk of developing nitrogen narcosis.

Helium is also used in a variety of other applications, including balloons, blimps, and cryogenics. It is a non-flammable gas that is ideal for these applications.