Which one of the following statements is true?

Options

A. Head of humerus bone articulates with acetabulum of pectoral girdle.
B. Head of humerus bone articulates with glenoid cavity of pectoral girdle.
C. Head of humerus bone articulates with a cavity called acetabulum of pelvic girdle.
D. Head of humerus bone articulates with a glenoid cavity of pelvic girdle.

Explanation

To determine which statement is true regarding the articulation of the humerus bone, we can analyze each statement step by step.

### Step-by-Step Solution:

1. **Understanding the Humerus Bone**: The humerus is the long bone in the upper arm. It has a rounded head that articulates with the shoulder girdle.

2. **Evaluating the First Statement**: The first statement claims that the head of the humerus articulates with the acetabulum of the pectoral girdle.
- **Analysis**: The acetabulum is actually part of the pelvic girdle, not the pectoral girdle. Therefore, this statement is false.

3. **Evaluating the Second Statement**: The second statement claims that the head of the humerus articulates with the glenoid cavity of the pectoral girdle.
- **Analysis**: This is correct. The head of the humerus fits into the glenoid cavity, forming a ball-and-socket joint, which allows for a wide range of motion.

4. **Evaluating the Third Statement**: The third statement claims that the head of the humerus articulates with the acetabulum of the pelvic girdle.
- **Analysis**: This is incorrect as the acetabulum is part of the pelvic girdle, and the humerus does not articulate with it.

5. **Evaluating the Fourth Statement**: The fourth statement claims that the head of the humerus articulates with the glenoid cavity of the pelvic girdle.
- **Analysis**: This is also incorrect. The glenoid cavity is part of the pectoral girdle, not the pelvic girdle.

6. **Conclusion**: The only true statement among the options provided is that the head of the humerus articulates with the glenoid cavity of the pectoral girdle.

### Final Answer:
The correct statement is: "The head of the humerus bone articulates with the glenoid cavity of the pectoral girdle."

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