One of the possible early sources of energy was/were

Options

A. `CO_(2)`
B. chlorophyll
C. green plants
D. UV rays and lightning.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for one of the possible early sources of energy on Earth before life originated.

2. **Analyzing Current Ecosystems**: In present ecosystems, green plants (producers) are the main source of energy as they perform photosynthesis, converting sunlight into chemical energy.

3. **Considering Early Earth Conditions**: The conditions on early Earth were drastically different from today. The atmosphere was reducing, lacking oxygen, and was characterized by unstable climatic conditions, including volcanic activity and frequent lightning.

4. **Identifying Potential Energy Sources**: Given the harsh conditions and the absence of life, we need to consider what could have provided energy in such an environment.

5. **Evaluating Options**:
- **CO2**: This is a substrate for photosynthesis but not a direct source of energy.
- **Chlorophyll**: This is a pigment involved in photosynthesis, not a source of energy itself.
- **Green Plants**: These are current energy sources but did not exist before life originated.
- **UV Rays and Lightning**: These natural phenomena could have provided energy in the form of radiation and electrical discharge.

6. **Conclusion**: The most plausible early sources of energy on Earth would have been UV rays and lightning, as they were present in the unstable conditions of early Earth.

**Final Answer**: One of the possible early sources of energy was UV rays and lightning.

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