You are answering a USMLE-style medical question. Question: A 33-year-old man presents to the emergency department with a cough. He states that 2 weeks ago, he had a fever, chills, and a cough, which his primary doctor treated with acetaminophen, ibuprofen, and rest. Since then, the patient’s symptoms have resolved with the exception of a chronic cough and a small amount of clear sputum that is occasionally laced with blood. The patient denies chest pain, shortness of breath, fever, or chills. The patient is otherwise healthy and is currently taking metformin and albuterol. His temperature is 98.3°F (36.8°C), blood pressure is 129/75 mmHg, pulse is 84/min, respirations are 15/min, and oxygen saturation is 99% on room air. Physical exam is notable for bilateral clear breath sounds, absence of lymphadenopathy on HEENT exam, and a normal oropharynx. Which of the following is the best next step in management? Options: A) Chest radiograph B) D-dimer C) Sputum culture D) Supportive care Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.