Question

Deep sea divers use a mixture of:

• A. Helium - Oxygen
• B. Nitrogen - Oxygen
• C. Hydrogen - Nitrogen
• D. Helium - Nitrogen

Hint:

Helium is less soluble in blood compared to nitrogen, reducing the risks for divers when breathing under high pressure.

Answer 1

The Correct Option is A

Step 1: Concept.
At great depth, nitrogen in ordinary air dissolves into the blood under high pressure and causes narcosis and decompression sickness risk.

Step 2: Pick the safe substitute.
Helium is light and inert, so it replaces nitrogen without causing narcosis, and it is mixed with oxygen so the diver still has something to breathe.

Step 3: Final Answer.
Deep sea divers breathe a Helium - Oxygen mixture.

Answer 2

Instead of judging each mixture on its own, group the wrong options by the single flaw that rules each one out, then see what is left standing.

1. Nitrogen - Oxygen: Fails because of narcosis. This is regular air, and its nitrogen becomes intoxicating under high pressure at depth.
2. Hydrogen - Nitrogen: Fails on two counts at once. Hydrogen is dangerously flammable, and nitrogen is still there to cause narcosis, plus there is no oxygen to breathe.
3. Helium - Nitrogen: Fails because it has no oxygen for the diver to breathe, and it still carries nitrogen, which causes narcosis anyway.
4. Helium - Oxygen: None of the flaws above apply here. Helium is inert and non-narcotic, it is not flammable, and oxygen is present for breathing, so this mixture clears every hazard the other three fail on.

Once the three flawed mixtures are ruled out for narcosis, flammability, or missing oxygen, only the helium-oxygen mixture is left.

So the correct answer is Helium - Oxygen.