Assertion :- Thymus undergoes no change even in old age.
Reason:- Thymus being a part of body's immune system, tends to persist throughout life.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false
D. If both assertion and reason are false.

Answer

**Step-by-Step Solution:**

1. **Understanding the Assertion**: The assertion states that the thymus undergoes no change even in old age. This implies that the thymus remains the same size and function throughout a person's life.

2. **Understanding the Reason**: The reason provided claims that the thymus is part of the body's immune system and thus persists throughout life. This suggests that because of its role in immunity, the thymus should remain unchanged.

3. **Analyzing the Thymus Gland**: The thymus gland is indeed a crucial part of the immune system, particularly in the development of T-cells, which are essential for adaptive immunity. However, it is important to note that the thymus does not remain unchanged throughout life.

4. **Changes in the Thymus with Age**: Research shows that the thymus gland undergoes involution (a process of degeneration) as a person ages. This means that the size and functionality of the thymus decrease over time, particularly after puberty.

5. **Impact on Immunity**: As the thymus shrinks and its function declines, the production of thymosine (the hormone produced by the thymus) decreases. This reduction leads to a weakened immune response in older individuals.

6. **Conclusion**: Both the assertion and the reason are incorrect. The thymus does undergo changes with age, specifically degeneration, and does not persist unchanged throughout life.

**Final Answer**: Both the assertion and the reason are false.

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