Which one of the following is correct description of a certain part of a normal human skeleton ?

Options

A. Parietal bone and the temporal bone of the skull are joined by fibrous joint
B. First vertebra is axis which articulates with the occipital condyles
C. The 9th and 10th pairs of ribs are called the floating ribs
D. Glenoid cavity is a depression to which the thigh bone articulates

Answer

To solve the question regarding the correct description of a certain part of a normal human skeleton, we will analyze each option provided:

### Step-by-Step Solution:

1. **Understanding the Options**:
- We have four options to evaluate:
- A. Parietal bone and temporal bone of the skull are joined by fibrous joint.
- B. First vertebral axis which articulates with occipital condyles.
- C. The 9th and 10th ribs of the pairs of ribs are called floating ribs.
- D. Clinoid cavity is a depression to which the thigh bone articulates.

2. **Evaluating Option A**:
- The parietal bone and temporal bone are indeed parts of the skull. They are joined by sutures, which are immovable fibrous joints. This statement is correct.

3. **Evaluating Option B**:
- The first vertebra is known as the atlas, not the axis. The atlas articulates with the occipital condyles of the skull. Therefore, this statement is incorrect.

4. **Evaluating Option C**:
- The 9th and 10th pairs of ribs are not floating ribs; they are considered false ribs. The floating ribs are actually the 11th and 12th pairs. Thus, this statement is also incorrect.

5. **Evaluating Option D**:
- The term "clinoid cavity" is incorrect in this context. The correct term is "glenoid cavity," which is a depression in the scapula where the head of the humerus (not the thigh bone) articulates. Therefore, this statement is incorrect.

6. **Conclusion**:
- After evaluating all the options, the only correct statement is Option A: "Parietal bone and temporal bone of the skull are joined by fibrous joint."

### Final Answer:
**Option A: Parietal bone and temporal bone of the skull are joined by fibrous joint.**

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