Obligatory water reabsorption takes place at

Options

A. PCT
B. DCT
C. Collecting duct
D. Both (A) and (B)

Answer

To solve the question regarding where obligatory water reabsorption takes place, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Water Reabsorption**:
- Water reabsorption in the kidneys can be categorized into two types: obligatory and facultative.
- Obligatory water reabsorption refers to the process where water is reabsorbed regardless of the body's hydration status.

2. **Identify the Locations of Water Reabsorption**:
- The primary sites of water reabsorption in the nephron are:
- Proximal Convoluted Tubule (PCT)
- Distal Convoluted Tubule (DCT)
- Collecting Duct

3. **Determine the Percentage of Water Reabsorption**:
- Approximately 65% of water reabsorption occurs in the PCT.
- About 20% of water reabsorption occurs in the DCT.
- The remaining 15% of water reabsorption is facultative and occurs in the collecting duct, depending on the body's hydration status.

4. **Conclusion on Obligatory Water Reabsorption**:
- Since obligatory water reabsorption occurs primarily in the PCT and partially in the DCT, the correct answer to the question is that it takes place at both the PCT and DCT.

5. **Final Answer**:
- The correct answer is **both A and B** (PCT and DCT).