You are answering a USMLE-style medical question. Question: A 32-year-old man comes to the physician because of a 2-day history of a tingling sensation in his right forearm. He reports that his symptoms started after he lifted heavy weights at the gym. Physical examination shows loss of sensation on the lateral side of the right forearm. Sensation over the thumb is intact. Range of motion of the neck is normal. His symptoms do not worsen with axial compression or distraction of the neck. Further examination of this patient is most likely to show weakness of which of the following actions? Options: A) Elbow flexion B) Forearm pronation C) Index finger flexion D) Wrist extension Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.