Assign reason to the following :
Helium is used by scuba divers.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Context**: Scuba divers often use a mixture of gases for breathing underwater. The primary gases used in scuba diving are nitrogen (N2), oxygen (O2), and helium (He).

2. **Identifying the Role of Helium**: Helium is included in the gas mixture primarily for its unique properties. It is less soluble in blood compared to nitrogen. This is an important factor because when divers descend to greater depths, the pressure increases, and the solubility of gases in the blood also increases.

3. **Explaining the Importance of Low Solubility**: The lower solubility of helium in blood reduces the risk of nitrogen narcosis and decompression sickness (also known as "the bends"). Nitrogen narcosis can impair a diver's mental state, while decompression sickness occurs when nitrogen bubbles form in the bloodstream as a diver ascends too quickly.

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