The human intestine is long because-

Options

A. Bacteria in food can be killed gradually
B. It provides more space for food storage
C. It increases surface area for absorption of food
D. None of the above

Answer

### Step-by-Step Solution:

1. **Understanding the Function of the Intestine**:
- The primary role of the intestine is to absorb nutrients from the food we consume. This is crucial for providing energy and essential nutrients to the body.

2. **Evaluating the Options**:
- The question provides four options regarding why the human intestine is long. We need to analyze each option to find the correct reason.

3. **Analyzing Option 1**:
- **Option 1**: "Bacteria in food can be killed gradually."
- This option is incorrect because the length of the intestine is not primarily for killing bacteria. The intestine's function is more about nutrient absorption.

4. **Analyzing Option 2**:
- **Option 2**: "It provides more space for food storage."
- This option is also incorrect. The human body does not store food in the intestine; instead, it absorbs nutrients and passes waste.

5. **Analyzing Option 3**:
- **Option 3**: "It increases surface area for absorption of food."
- This option is correct. The length of the intestine, particularly the small intestine, is designed to maximize the surface area for absorption. The presence of structures like villi (finger-like projections) further increases this surface area, allowing for more efficient nutrient absorption.

6. **Analyzing Option 4**:
- **Option 4**: "None of the above."
- Since we have identified option 3 as correct, this option is incorrect.

7. **Conclusion**:
- The correct answer is **Option 3: It increases surface area for absorption of food**. The long length of the intestine, along with its structural adaptations, facilitates the efficient absorption of nutrients.