I. The lymph nodes are small solid structures
II. The thymus is quite large at the time of birth
III. Spleen is secondary lymphoid organ
IV. MALT constitutes about 50% of the lymphoid tissue in human body.
Identify the correct statement :-

Options

A. I, III only
B. III only
C. I, II, IV only
D. All are correct

Answer

To solve the question, we need to evaluate each of the four statements regarding lymphoid organs and tissues to identify which ones are correct.

### Step-by-Step Solution:

1. **Evaluate Statement I: "The lymph nodes are small solid structures."**
- Lymph nodes are indeed small, solid structures that play a crucial role in the immune system by filtering lymph fluid and housing lymphocytes.
- **Conclusion:** This statement is **correct**.

2. **Evaluate Statement II: "The thymus is quite large at the time of birth."**
- The thymus is a primary lymphoid organ that is relatively large at birth, as it is essential for the development of T lymphocytes. However, its size decreases after puberty.
- **Conclusion:** This statement is **correct**.

3. **Evaluate Statement III: "Spleen is a secondary lymphoid organ."**
- The spleen is indeed classified as a secondary lymphoid organ. It filters blood and helps in the immune response.
- **Conclusion:** This statement is **correct**.

4. **Evaluate Statement IV: "MALT constitutes about 50% of the lymphoid tissue in the human body."**
- MALT (mucosa-associated lymphoid tissue) is a significant component of the immune system and is present in mucosal linings. It does indeed constitute a substantial portion of lymphoid tissue, often cited as around 50%.
- **Conclusion:** This statement is **correct**.

### Final Answer:
All four statements are correct.