[A] : Molecules of fatty acid, glycerol, sugars and amino acids are absorbed by the huge number of villi that line the intestinal wall.
[R]: Absorption involves active transport and requires an expenditure of cellular energy

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, we need to analyze the assertion and reason provided, and determine their validity and relationship.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "molecules of fatty acids, glycerol, sugars, and amino acids are absorbed by the huge number of villi that line the intestinal wall."
- This statement is true. Villi are small, finger-like projections in the intestine that increase the surface area for absorption of nutrients.

2. **Understanding the Reason**:
- The reason states that "absorption involves active transport and requires an expenditure of cellular energy."
- This statement is also true. Active transport is a process that moves substances against their concentration gradient and requires energy, typically in the form of ATP.

3. **Analyzing the Relationship**:
- The assertion describes the process of nutrient absorption in the intestines, while the reason explains one of the mechanisms (active transport) involved in absorption.
- However, not all absorption processes rely solely on active transport; some nutrients can be absorbed through passive diffusion or facilitated diffusion as well.

4. **Conclusion**:
- Both the assertion and reason are true, but the reason does not serve as a correct explanation for the assertion since absorption can occur through multiple mechanisms, not just active transport.
- Therefore, the correct option is that both assertion and reason are true, but the reason is not the correct explanation of the assertion.

### Final Answer:
The correct option is: **Both assertion and reason are true, but reason is not the correct explanation of assertion.**

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