Sigmoid notch of olecranon process is found in
(a) Tibio-fibula
(b) Femur
(c) Radio-ulna
(d) Humerus

Options

A. Tibio-fibula
B. Femur
C. Ratio-ulna
D. Humerus.

Answer

To determine where the sigmoid notch of the olecranon process is found, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Terms**:
- The "sigmoid notch" is a specific anatomical feature, which is a large depression.
- The "olecranon process" is a bony prominence of the ulna, which is one of the two bones in the forearm.

2. **Identify the Location of the Sigmoid Notch**:
- The sigmoid notch is located at the upper extremity of the ulna. This means it is part of the ulna bone, specifically at the elbow joint.

3. **Determine the Function of the Sigmoid Notch**:
- The sigmoid notch allows the ulna to fit into the trochlea of the humerus, forming part of the elbow joint. This is crucial for the movement of the arm.

4. **Evaluate the Options**:
- (a) Tibio-fibula: This refers to the bones of the lower leg and does not contain a sigmoid notch.
- (b) Femur: This is the thigh bone and does not have a sigmoid notch.
- (c) Radio-ulna: This refers to the radius and ulna together, but the sigmoid notch specifically pertains to the ulna.
- (d) Humerus: This is the upper arm bone and does not contain a sigmoid notch.

5. **Conclusion**:
- Since the sigmoid notch is specifically a feature of the ulna, the correct answer is (c) Radio-ulna, as it includes the ulna where the sigmoid notch is located.

### Final Answer:
(c) Radio-ulna