The strength of the bones is due to  

Options

A. calcium salts & collagen fibres
B. sodium salts & elastin
C. collagen & potassium salts
D. reticular fibres & collagen fibres

Answer

To answer the question "The strength of the bones is due to:", we need to analyze the components that contribute to bone strength.

### Step-by-Step Solution:

1. **Understanding Bone Composition**:
- Bones are composed of both organic and inorganic materials. The organic component primarily includes collagen fibers, while the inorganic component consists mainly of mineral salts.

2. **Identifying Key Components**:
- The two main components that provide strength to bones are:
- **Collagen Fibers**: These are protein fibers that provide flexibility and tensile strength to the bone structure.
- **Calcium Salts**: These are inorganic minerals, primarily hydroxyapatite, which provide hardness and compressive strength to the bones.

3. **Evaluating the Options**:
- **Calcium salts and collagen fiber**: This option includes both key components that contribute to bone strength.
- **Sodium salts and elastin**: Sodium does not significantly contribute to bone strength, and elastin is more associated with elastic tissues, not bones.
- **Collagen and potassium salts**: While collagen is important, potassium salts do not contribute to bone strength.
- **Reticular fibers and collagen fibers**: Reticular fibers are not a significant component of bone structure.

4. **Conclusion**:
- The correct answer is **calcium salts and collagen fiber**, as both are essential for providing strength and structure to bones.

### Final Answer:
The strength of the bones is due to **calcium salts and collagen fiber**.