You are answering a USMLE-style medical question. Question: A 32-year-old male presents to the emergency department because of fever and diarrhea. He was in his normal state of health until 2 weeks ago when he went abroad on a vacation. During his trip he went kayaking, visited spas, interacted with local animals, and ate local foods. Since returning he has had 3-day history of fever, cough, headache, and diarrhea. He drinks socially and has a 15-pack-year history of smoking. On presentation his temperature is 102.3°F (39.1°C), blood pressure is 105/62 mmHg, pulse is 91/min, respirations are 18/min, and O2 saturation is 91% on room air. Chest exam reveals fine crackles on auscultation. Chest radiograph reveals patchy infiltrates in both lungs and labs reveal mild hyponatremia and mild elevation of AST/ALT levels. The organism that is most likely responsible for this patient's symptoms is associated with which of the following characteristics? Options: A) Can form an endospore B) Has no cell wall C) Is more common in parrot owners D) Is transmitted by air conditioning Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.