If a piece of bone such as femur of frog is kept in dilute HCl for about a week . It will

Options

A. assume black colour
B. shrink in size
C. turn flexible
D. crack into pieces

Explanation

### Step-by-Step Solution:

1. **Understanding Bone Composition**:
- Bones are made up of two main components: organic and inorganic materials.
- The organic components include proteins and collagen, while the inorganic components primarily consist of calcium phosphate and other mineral salts.

2. **Effect of Dilute HCl on Bone**:
- When a piece of bone, such as the femur of a frog, is placed in dilute hydrochloric acid (HCl), the acid reacts with the inorganic components of the bone.
- The dilute HCl will dissolve the inorganic salts (calcium phosphate) present in the bone.

3. **Duration of Exposure**:
- Keeping the bone in dilute HCl for about a week allows sufficient time for the acid to effectively dissolve the inorganic components.

4. **Result of the Reaction**:
- As the inorganic components are dissolved, what remains are the organic components of the bone.
- This process is known as decalcification, which leads to the removal of calcium and phosphate salts.

5. **Final Outcome**:
- After the inorganic components are removed, the bone will lose its rigidity and become flexible due to the presence of only the organic material.

6. **Conclusion**:
- Therefore, the correct outcome of keeping a piece of frog femur bone in dilute HCl for a week is that it will turn flexible.