Air is a mixture of various gases. One of the gases is 21% part of the air and is essential for the survival of human beings. This gas is

Options

A. nitrogen
B. ozone
C. oxygen
D. argon

Answer

**Step-by-Step Solution:**

1. **Understanding the Composition of Air**: Air is not a single substance but a mixture of various gases. The main gases found in air include nitrogen, oxygen, carbon dioxide, and argon.

2. **Identifying the Major Components**:
- Nitrogen makes up about 78% of the air.
- Oxygen constitutes approximately 21% of the air.
- The remaining 1% is made up of other gases, including argon and carbon dioxide.

3. **Focusing on the Essential Gas**: The question specifies that the gas in question is essential for the survival of human beings and constitutes 21% of the air.

4. **Identifying the Correct Gas**:
- Since we know that oxygen is the gas that is vital for human survival and is present in the air at 21%, we can conclude that the answer to the question is oxygen.

5. **Final Answer**: Therefore, the gas that is 21% of the air and essential for human survival is **oxygen**.

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