Assertion : Change in structure of chromosome is called chromosomal aberration.
Reason : Substitution is an example of chromosomal aberration.

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 Text Solution:**

1. **Understanding the Assertion**: The assertion states that "Change in structure of chromosome is called chromosomal aberration." This is a true statement. Chromosomal aberrations refer to any changes in the normal structure or number of chromosomes, which can affect genetic information.

2. **Understanding the Reason**: The reason given is "Substitution is an example of chromosomal aberration." However, this statement is not accurate. Substitution typically refers to a type of mutation where one base pair is replaced by another in the DNA sequence, which is a point mutation, not a chromosomal aberration.

3. **Evaluating the Relationship**: Since the assertion is true but the reason is false, the two statements do not support each other. The assertion stands correct on its own, but the reason does not provide a valid explanation.

4. **Conclusion**: Therefore, the correct evaluation of the assertion and reason is that the assertion is true, but the reason is false.

**Final Answer**: The assertion is true, but the reason is false.

---