In the early earth, water and `CO_(2)` were produced by the combination of `O_(2)` with

Options

A. ammonia and methane
B. hydrogen
C. organic matter
D. sulphates and nitrates

Answer

To solve the question, "In the early earth, water and CO₂ were produced by the combination of O₂ with," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Early Earth's Atmosphere**:
- In the early Earth, the atmosphere was quite different from what we have today. It lacked free oxygen (O₂) and was composed mainly of gases like methane (CH₄), ammonia (NH₃), hydrogen (H₂), and others.

2. **Identify the Role of Oxygen**:
- The question asks about the combination of O₂. Since the early atmosphere did not have free O₂, we need to consider how O₂ could have been produced or reacted in that environment.

3. **Consider Possible Reactions**:
- The free oxygen that was eventually present could react with various gases. The most relevant reactions would involve O₂ reacting with methane (CH₄) and ammonia (NH₃) to produce water (H₂O) and carbon dioxide (CO₂).

4. **Evaluate the Options**:
- Option A: Ammonia and methane - This is a plausible combination since O₂ could react with these gases to produce water and CO₂.
- Option B: Hydrogen - While hydrogen is abundant, it does not directly combine with O₂ to produce water and CO₂.
- Option C: Organic matter - This is too vague and does not specifically indicate a reaction with O₂.
- Option D: Sulfates and Nitrates - These compounds are not relevant to the production of water and CO₂ in the context of early Earth.

5. **Conclusion**:
- Based on the reactions that would have occurred in the early atmosphere, the correct answer is **Option A: Ammonia and methane**. O₂ would have reacted with these gases to produce water and carbon dioxide.

### Final Answer:
**Option A: Ammonia and methane.**

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