[A] : Peyer's patches are derivatives of lymphoid tissue.
[R]: These are most numerous in the region of colon.

Options

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

Answer

To solve the question regarding Peyer's patches and their location, we will analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding Peyer's Patches**:
- Peyer's patches are small masses of lymphatic tissue. They play a crucial role in the immune system by monitoring intestinal bacteria and preventing the growth of pathogenic bacteria.

**Hint**: Remember that Peyer's patches are part of the immune system and are related to lymphatic tissue.

2. **Location of Peyer's Patches**:
- These patches are primarily found in the ileum, which is the last part of the small intestine. They are not predominantly located in the colon.

**Hint**: Focus on the specific region of the small intestine where Peyer's patches are most abundant.

3. **Evaluating the Assertion**:
- The assertion states that "Peyer's patches are derivatives of lymphoid tissue." This is true because they are indeed formed from lymphatic tissue.

**Hint**: Consider the definition of Peyer's patches and their origin in the lymphatic system.

4. **Evaluating the Reason**:
- The reason states that "These are most numerous in the region of colon." This is false, as Peyer's patches are most numerous in the ileum, not the colon.

**Hint**: Recall the anatomical location of Peyer's patches to determine the accuracy of the statement about their abundance.

5. **Conclusion**:
- Since the assertion is true and the reason is false, the correct answer is that the assertion is true while the reason is false.

### Final Answer:
The correct option is that the assertion is true, but the reason is false.