Which of the following is not correct about acetabulum?
(a) It is a part of pectoral girdle.
(b) It articulates with the head of femur to form the hip joint.
(c) It is formed by the fusion of ilium, ischium and pubis.
(d) It is a part of pelvic girdle.

Options

A. It is a part of pectoral girdle.
B. It articulates with the head of femur to form the hip joint.
C. It is formed by the fusion of ilium, ischium and pubis.
D. It is a part of pelvic girdle.

Answer

To solve the question regarding the acetabulum, we need to evaluate each of the provided options to determine which statement is incorrect.

### Step-by-Step Solution:

1. **Understanding Acetabulum**: The acetabulum is a cup-shaped socket in the hip bone that articulates with the head of the femur to form the hip joint. It plays a crucial role in the skeletal system.

2. **Analyzing Option (a)**: "It is a part of pectoral girdle."
- The pectoral girdle consists of the clavicle and scapula, which are involved in connecting the upper limb to the trunk. The acetabulum is not part of this structure. Therefore, this statement is **incorrect**.

3. **Analyzing Option (b)**: "It articulates with the head of femur to form the hip joint."
- This statement is true. The acetabulum does indeed articulate with the head of the femur, forming the hip joint.

4. **Analyzing Option (c)**: "It is formed by the fusion of ilium, ischium and pubis."
- This statement is also true. The acetabulum is formed by the fusion of three bones: ilium, ischium, and pubis.

5. **Analyzing Option (d)**: "It is a part of pelvic girdle."
- This statement is true as well. The acetabulum is located in the pelvic girdle, which is made up of the coxal bones formed by the fusion of the ilium, ischium, and pubis.

6. **Conclusion**: The only statement that is not correct about the acetabulum is option (a), which states that it is a part of the pectoral girdle.

### Final Answer:
**(a) It is a part of pectoral girdle.**

---