The correct answer is D. Helium is less soluble in blood than nitrogen at high pressure.
When a diver descends, the pressure of the water increases. This increase in pressure causes the gases in the diver’s blood to dissolve more easily. Nitrogen is one of the gases that dissolves in the blood. As the diver descends, more and more nitrogen dissolves in the blood. If the diver ascends too quickly, the nitrogen bubbles out of the blood too quickly, which can cause decompression sickness, also known as the bends.
Helium is less soluble in blood than nitrogen. This means that it does not dissolve in the blood as easily. This makes helium a safer gas for deep sea divers to breathe.
A. Less poisonous than nitrogen: This is true, but it is not the main reason why helium is added to the oxygen supply of deep sea divers.
B. Lighter than nitrogen: This is also true, but it is not the main reason why helium is added to the oxygen supply of deep sea divers.
C. Readily miscible with oxygen: This is not true. Helium is less miscible with oxygen than nitrogen. This means that it is more difficult for helium and oxygen to mix together. This can make it difficult for the diver to breathe.