[A]: Isolation prevents inbreeding among the otherwise potential mates.
[R]: It preserves variations which can lead to speciation.

Options

A. (a) If both A and R are true and R is the correct explanation of A
B. (b) If both A and R are true but R is not the correct explanation of A
C. (c) If A is true and R is false
D. (d) If both A and R are false

Answer

To solve the assertion-reason question, we will analyze both the assertion (A) and the reason (R) step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that "Isolation prevents inbreeding among the otherwise potential mates."
- This means that when organisms are isolated, they cannot mate with each other, which reduces the chances of inbreeding. Inbreeding occurs when closely related individuals breed, which can lead to an increase in homozygosity and the expression of deleterious alleles.

2. **Evaluating the Truth of the Assertion**:
- The assertion is true. Isolation can be geographical, ecological, or reproductive. By preventing potential mates from coming together, isolation effectively reduces inbreeding.

3. **Understanding the Reason (R)**:
- The reason states that "It preserves variations which can lead to speciation."
- This suggests that by preventing inbreeding, isolation helps maintain genetic diversity (variations) within a population. Genetic diversity is crucial for the adaptability and survival of species.

4. **Evaluating the Truth of the Reason**:
- The reason is also true. When inbreeding is prevented, the genetic variations (especially heterozygous alleles) are preserved. This genetic diversity can lead to speciation, which is the formation of new species over time due to evolutionary processes.

5. **Connecting Assertion and Reason**:
- The reason provided explains why the assertion is true. By preventing inbreeding, isolation helps maintain genetic variation, which is essential for speciation.

6. **Conclusion**:
- Both the assertion and the reason are true, and the reason correctly explains the assertion. Therefore, the correct answer is that both A and R are true, and R is the correct explanation of A.

### Final Answer:
- The correct answer is: **A is true, R is true, and R is the correct explanation of A.**

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