What is the percentage of oxygen in atmosphere ?

Options

A. 21
B. 78
C. 0.9
D. 0.1

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the percentage of oxygen present in the atmosphere.

2. **Identifying the Options**: The options provided are:
- Option 1: 21%
- Option 2: 78%
- Option 3: 0.9%
- Option 4: 0.1%

3. **Recalling Atmospheric Composition**: To answer the question, we need to recall the composition of the Earth's atmosphere. The atmosphere is primarily composed of nitrogen and oxygen, along with trace amounts of other gases.

4. **Knowing the Key Percentages**:
- Nitrogen (N₂) constitutes about 78% of the atmosphere.
- Oxygen (O₂) constitutes about 21% of the atmosphere.
- Other gases, including argon (Ar), make up about 0.9%, and trace gases like hydrogen and neon account for about 0.1%.

5. **Selecting the Correct Answer**: Based on the known composition of the atmosphere, the correct answer to the question is:
- **21%** for oxygen.

6. **Conclusion**: Therefore, the percentage of oxygen in the atmosphere is **21%**.

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