You are answering a USMLE-style medical question. Question: A 37-year-old man with no significant past medical history is rear-ended in a motor vehicle accident. He reported significant neck pain to emergency responders, but otherwise denies weakness, numbness or tingling in his extremities. His vitals on presentation to the ED are HR 90, BP 140/80, RR 20, SpO2 98%. What is the most appropriate next step upon presentation to the emergency room? Options: A) Lateral cervical film B) Cervical immobilization C) IV methylprednisolone D) Observation overnight Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.