Assertion : The earliest organisms were anaerobes, having arisen in a sea of organic molecules, and were chemoheterotrophs
Reason : Before the supply of organic molecules exhausted, some of the heterotrophs might have evolved into autotrophs.

Options

A. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion, then mark (1)
B. If both Assertion and Reason are true ,but the Reason is not the correct explanation of the Assertion, then mark (2).
C. If Assertion is true, but Reason is false , then mark (3)
D. If both Assertion and Reason are false. , then mark (4)

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that the earliest organisms were anaerobes that arose in a sea of organic molecules and were chemoheterotrophs.
- **Anaerobes** are organisms that can live without oxygen.
- **Chemoheterotrophs** are organisms that obtain their energy by consuming organic compounds produced by other organisms.

2. **Evaluating the Reason**:
- The reason given is that before the supply of organic molecules exhausted, some of the heterotrophs might have evolved into autotrophs.
- **Autotrophs** are organisms that can produce their own food from inorganic substances.

3. **Analyzing the Primitive Earth Conditions**:
- The early Earth had no free oxygen, which means only anaerobic organisms could survive.
- The first life forms were likely heterotrophs, relying on organic molecules available in their environment.

4. **Linking Assertion and Reason**:
- The assertion correctly describes the nature of the earliest life forms as anaerobic and chemoheterotrophic.
- The reason suggests a transition from heterotrophy to autotrophy as organic molecules became scarce, which is a plausible evolutionary step.

5. **Conclusion**:
- Both the assertion and the reason are true. However, the reason does not directly explain the assertion. The assertion describes the initial state of life, while the reason discusses a subsequent evolutionary change.

### Final Answer:
- Both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.

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