Assertion : When you open your mouth wide, you can move your lower jaw away from your head, but you cannot move your upper jaw.
Reason : The joint between the upper jaw and rest of the head is a fixed joint whereas the joint between the lower jaw and rest of the head is movable joint.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Answer

**Step-by-Step Solution:**

1. **Understanding the Assertion**: The assertion states that when you open your mouth wide, you can move your lower jaw away from your head, but you cannot move your upper jaw. This means that the lower jaw (mandible) is capable of movement while the upper jaw (maxilla) is not.

2. **Understanding the Reason**: The reason provided explains why this is the case. It states that the joint between the upper jaw and the rest of the head is a fixed joint, while the joint between the lower jaw and the rest of the head is a movable joint.

3. **Identifying the Joints**:
- The upper jaw (maxilla) is connected to the skull by a fixed joint, which does not allow for movement. This is why the upper jaw remains stationary when you open your mouth wide.
- The lower jaw (mandible) is connected to the skull by a movable joint called the temporomandibular joint (TMJ). This joint allows for the movement necessary for actions like chewing and speaking.

4. **Conclusion**: Since the assertion is correct (the lower jaw can move while the upper jaw cannot) and the reason is also correct (the upper jaw is fixed while the lower jaw is movable), we conclude that both the assertion and the reason are true, and the reason correctly explains the assertion.

5. **Final Answer**: Both assertion and reason are true, and the reason is true for the assertion.

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