**Core Concept**
Colles' fracture is a type of fracture at the distal end of the radius bone in the forearm. This fracture typically occurs when a person falls onto an outstretched hand, causing a displacement of the bone fragments. The fracture is characterized by a distinct wrist deformity.

**Why the Correct Answer is Right**
The correct answer is related to the clinical presentation of Colles' fracture. A classic feature of this fracture is the presence of a dorsal angulation of the distal fragment, leading to a 'dinner fork' deformity. This occurs due to the displacement of the bone fragments, which results in an abnormal alignment of the wrist.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because a Colles' fracture typically does not present with volar angulation of the distal fragment. Instead, it is characterized by dorsal angulation.
**Option B:** This option is incorrect because the presence of a 'gunstock' deformity is more characteristic of a Smith's fracture, which is a type of fracture at the distal end of the radius with volar angulation.
**Option C:** This option is incorrect because a Colles' fracture is typically associated with a 'dinner fork' deformity, not a 'sail sign'. The 'sail sign' is more characteristic of a scaphoid fracture.

**Clinical Pearl / High-Yield Fact**
One key feature to remember when diagnosing a Colles' fracture is the presence of a 'dinner fork' deformity, which is a result of the dorsal angulation of the distal fragment. This can be remembered using the mnemonic 'DR DINNER', where each letter represents a key feature of the fracture.

**Correct Answer:** D. Dinner fork deformity