The odd one out in the following is
(I).spleen and peyer's patches
(II).spleen and thymus
(III).liver and spleen
(IV).thymus and peyer's patches
Codes

Options

A. I and IV
B. III and II
C. Only III
D. Only II

Answer

To determine the odd one out among the given pairs, we need to analyze each option based on whether the structures mentioned are lymphoid tissues or not.

### Step-by-Step Solution:

1. **Analyze Option I: Spleen and Peyer's Patches**
- Both the spleen and Peyer's patches are lymphoid tissues.
- The spleen is a secondary lymphoid organ, and Peyer's patches are also considered secondary lymphoid tissues found in the intestine.

2. **Analyze Option II: Spleen and Thymus**
- The spleen is a secondary lymphoid organ.
- The thymus is a primary lymphoid organ where T-lymphocytes mature.
- Both structures are involved in the immune response, but they belong to different categories of lymphoid organs.

3. **Analyze Option III: Liver and Spleen**
- The spleen is a secondary lymphoid organ.
- The liver, while it plays a role in immune function (such as filtering blood and presenting antigens), is not classified as a lymphoid tissue.
- This pair includes one lymphoid organ (spleen) and one non-lymphoid organ (liver).

4. **Analyze Option IV: Thymus and Peyer's Patches**
- The thymus is a primary lymphoid organ.
- Peyer's patches are secondary lymphoid organs.
- Both structures are involved in the immune system, but again, they belong to different categories.

### Conclusion:
From the analysis, Option III (Liver and Spleen) is the odd one out because it includes the liver, which is not a lymphoid tissue, while all the other options consist of lymphoid tissues.

### Final Answer:
The odd one out is **Option III: Liver and Spleen**.

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