Assertion `:-` Small intestine is very long and has plica circularis & villi
Reason `:` All these increase internal surface area of small intestine for efficient food absorption.

Options

A. If both Assertion & Reason are True & the Reasonn is a correct explanation of the Assertion .
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are false.

Answer

To solve the assertion and reason question regarding the small intestine, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Assertion**:
- The assertion states that "Small intestine is very long and has plica circularis & villi."
- This is true. The small intestine is indeed long (approximately 6 meters in adults) and contains structures called plica circularis (circular folds) and villi (small finger-like projections).

2. **Understand the Reason**:
- The reason states that "All these increase internal surface area of small intestine for efficient food absorption."
- This is also true. The presence of plica circularis and villi significantly increases the surface area of the small intestine, which is crucial for the absorption of nutrients.

3. **Evaluate the Relationship**:
- We need to determine if the reason correctly explains the assertion.
- The assertion describes the physical characteristics of the small intestine, while the reason explains the functional significance of these characteristics. Since the increased surface area due to plica circularis and villi directly contributes to efficient food absorption, the reason is indeed a correct explanation of the assertion.

4. **Conclusion**:
- Both the assertion and the reason are true, and the reason is the correct explanation for the assertion. Therefore, the correct answer is option A: "Both assertion and reason are true, and reason is the correct explanation of assertion."