What is the percentage of oxygen by volume in the atmosphere?

Options

A. `14%`
B. `23%`
C. `20.9%`
D. `79%`

Explanation

To find the percentage of oxygen by volume in the atmosphere, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Composition of the Atmosphere**:
The atmosphere is composed of various gases, with nitrogen (N2) being the most abundant.

2. **Identify the Major Components**:
- Nitrogen (N2): approximately 78%
- Oxygen (O2): approximately 21%
- Other gases (such as argon, carbon dioxide, etc.): less than 1%

3. **Focus on Oxygen**:
The question specifically asks for the percentage of oxygen in the atmosphere.

4. **State the Percentage**:
The percentage of oxygen by volume in the atmosphere is approximately 21%.

5. **Conclusion**:
Therefore, the answer to the question is that the percentage of oxygen by volume in the atmosphere is 21%.

### Final Answer:
The percentage of oxygen by volume in the atmosphere is approximately 21%.

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