Atmosphere of primordial earth lacked

Options

A. Ammonia
B. Hydrogen
C. Methane
D. Oxygen

Answer

### Step-by-Step Solution:

1. **Understanding Primordial Earth**: The question refers to the atmosphere of primordial Earth, which is believed to have existed around 4.5 to 5 billion years ago. This was a time when the Earth was still in its early stages of formation.

2. **Identifying Atmospheric Components**: The primordial atmosphere is thought to have contained various gases. Commonly accepted components include methane (CH4), ammonia (NH3), hydrogen (H2), and water vapor (H2O).

3. **Analyzing the Options**:
- **Ammonia (NH3)**: This gas was present in the primordial atmosphere.
- **Hydrogen (H2)**: Hydrogen was also abundant in the early atmosphere.
- **Methane (CH4)**: Methane was another gas that was present.
- **Oxygen (O2)**: Free oxygen was notably absent in the primordial atmosphere.

4. **Conclusion**: After evaluating the gases present in the primordial atmosphere, it is clear that while ammonia, hydrogen, and methane were present, free oxygen was not. Therefore, the correct answer to the question is that the atmosphere of primordial Earth lacked oxygen.

### Final Answer:
The atmosphere of primordial Earth lacked **oxygen**.

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