**Core Concept**
The child's symptoms are suggestive of a possible radial nerve injury, commonly known as "nursemaid's elbow" or radial head subluxation. This condition typically occurs in young children due to a sudden pull on the extended arm, leading to a partial dislocation of the radial head.

**Why the Correct Answer is Right**
The child is holding the forearm in a pronated position and refusing to move the affected extremity, which is a classic presentation of radial head subluxation. This occurs because the radial head is partially dislocated from its normal position, causing pain and discomfort. The pronated position is often adopted to minimize pain and discomfort. The management of radial head subluxation involves a simple reduction maneuver, where the affected arm is gently flexed and supinated, allowing the radial head to return to its normal position.

**Why Each Wrong Option is Incorrect**
**Option A:**
This option is incorrect because it does not address the underlying cause of the child's symptoms. A thorough examination and history are essential to diagnose radial head subluxation, and a simple X-ray may not be sufficient.

**Option B:**
This option is incorrect because it may exacerbate the injury. The child's forearm should be gently flexed and supinated, not extended or pronated.

**Option C:**
This option is incorrect because it does not address the child's symptoms. The child is not likely to have a fracture or a dislocation that requires immobilization.

**Option D:**
This option is incorrect because it does not address the child's symptoms. The child's refusal to move the affected extremity suggests a need for a specific management approach, such as reduction of the radial head subluxation.

**Clinical Pearl / High-Yield Fact**
Radial head subluxation is a common condition in young children and can be managed with a simple reduction maneuver. It is essential to recognize the classic presentation of this condition, which includes holding the forearm in a pronated position and refusing to move the affected extremity.

**Correct Answer: C. Immobilization is not required, but a reduction maneuver may be needed.**