Which of the following glands is large sized at birth but reduces in size with ageing ?

Options

A. Pineal
B. Pituitary
C. Thymus
D. Thyroid

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which gland is large at birth but decreases in size as a person ages.

2. **Identifying the Options**: The options given are:
- a. Penial
- b. Pituitary
- c. Thymus
- d. Thyroid

3. **Analyzing Each Option**:
- **Penial Gland**: This gland is not known for size changes related to age; it mainly functions in the production of melatonin.
- **Pituitary Gland**: This gland is relatively small at birth and grows to its adult size, so it does not fit the criteria.
- **Thyroid Gland**: The thyroid gland also does not significantly decrease in size with age; it maintains its size throughout life.
- **Thymus Gland**: The thymus is known to be large at birth and plays a crucial role in the immune system, particularly in the maturation of T-lymphocytes. It significantly decreases in size after puberty.

4. **Conclusion**: Based on the analysis, the gland that is large at birth and reduces in size with aging is the **Thymus Gland**.

5. **Final Answer**: The correct option is **c. Thymus**.

---