Humerus with its rounded upper end (head) articulates into

Options

A. acromion process
B. deltoid cavity
C. glenoid cavity
D. acetabulum.

Explanation

To answer the question about where the rounded upper end (head) of the humerus articulates, follow these steps:

1. **Identify the Humerus**: The humerus is the long bone of the upper arm, and its upper end is rounded, known as the head of the humerus.

2. **Understand the Joint Involved**: The head of the humerus forms a joint with another bone. In this case, it articulates with the scapula, which is the shoulder blade.

3. **Locate the Glenoid Cavity**: The specific part of the scapula that the head of the humerus articulates with is called the glenoid cavity (or glenoid fossa). This cavity is a shallow depression that allows for the ball-and-socket joint formation.

4. **Visualize the Joint**: The shoulder joint is a ball-and-socket joint, where the rounded head of the humerus fits into the glenoid cavity of the scapula, allowing for a wide range of motion.

5. **Conclusion**: Therefore, the rounded upper end (head) of the humerus articulates with the glenoid cavity of the scapula.

**Final Answer**: The head of the humerus articulates into the glenoid cavity of the scapula.

---