**Core Concept**
A green-stick fracture is a type of non-displaced fracture that occurs in children's bones, characterized by a bending or incomplete break. This is due to the flexible nature of growing bones, which can absorb the force of the injury and deform without fracturing completely.

**Why the Correct Answer is Right**
In children, the bones are still growing and have a higher proportion of cartilage and less calcified tissue. When a force is applied to a growing bone, it can cause the bone to bend or deform, leading to a green-stick fracture. This type of fracture is common in the forearm, particularly the ulna, and is often seen in children who fall onto an outstretched hand.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because a green-stick fracture is not a complete break in the bone, unlike a comminuted fracture.
**Option B:** This option is incorrect because a green-stick fracture is not a type of stress fracture, which occurs due to repetitive stress or overuse.
**Option C:** This option is incorrect because a green-stick fracture is not a type of avulsion fracture, which occurs when a small piece of bone is pulled away from the main bone.

**Clinical Pearl / High-Yield Fact**
A green-stick fracture is often associated with a characteristic "bent" or "angled" appearance of the bone on X-ray, which can be a clue to its diagnosis. It is essential to consider the age of the patient and the mechanism of injury when evaluating a child with a suspected fracture.

**Correct Answer:** C. **Bending or incomplete break in a child's bone.**