Select the necessary supplement for strengthening of bones.

Options

A. Phosphorus
B. Calcium
C. Vitamin D
D. All of these

Explanation

To answer the question regarding the necessary supplement for strengthening bones, we can analyze the options provided step by step.

### Step-by-Step Solution:

1. **Identify the Options**: The question presents four options, which we will evaluate one by one to determine their relevance to bone health.

2. **Evaluate Option A - Phosphorus**:
- Phosphorus is a mineral that is part of calcium phosphate, which is a major component of bone.
- It helps in maintaining bone mass and supports overall bone health.
- Conclusion: Phosphorus is necessary for strengthening bones.

3. **Evaluate Option B - Calcium**:
- Calcium is well-known for its role in bone health.
- It contributes to the hardness and strength of bones.
- Conclusion: Calcium is essential for strengthening bones.

4. **Evaluate Option C - Vitamin D**:
- Vitamin D is crucial for the absorption of calcium in the body.
- It helps in the development and maintenance of healthy bones.
- Conclusion: Vitamin D is vital for bone health.

5. **Final Conclusion**:
- Since all three options (Phosphorus, Calcium, and Vitamin D) play significant roles in bone health, the correct answer is that all of these supplements are necessary for strengthening bones.

### Final Answer: All of these (Phosphorus, Calcium, and Vitamin D).

---