**Core Concept**
The given scenario describes a common type of injury resulting from a fall onto an outstretched hand, which is a classic mechanism for a specific type of fracture. This type of injury is often associated with the distal radius, a bone in the forearm that forms the lateral part of the wrist.

**Why the Correct Answer is Right**
When a person falls onto an outstretched hand, the force of the impact is transmitted up the forearm and into the wrist, causing a fracture of the distal radius. This type of fracture is often referred to as a Colles' fracture, which is a displaced fracture of the distal end of the radius. The distal radius is particularly susceptible to fracture due to its thin cortical bone and the fact that it bears a significant amount of weight and stress.

**Why Each Wrong Option is Incorrect**
* **Option A:** The scaphoid bone, while also located in the wrist, is not typically the primary bone to fracture in this type of fall.
* **Option B:** The ulna, a bone in the forearm, can be involved in fractures of the elbow or forearm, but it is not the most common bone to fracture in a fall onto an outstretched hand.
* **Option D:** The humerus, the long bone of the upper arm, is not typically involved in wrist or forearm fractures.

**Clinical Pearl / High-Yield Fact**
In cases of suspected Colles' fracture, it is essential to obtain a thorough history and perform a careful physical examination to assess for associated injuries, such as median nerve compression or distal radioulnar joint instability.

**Correct Answer: C. Distal Radius.**