This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
[{'content': 'Trichomoniasis is transmitted through which stage \nSelect and explain. \nA. Cyst, B. Oocyst, C. Sporozoite, D. Trophozoite', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Trichomonas vaginalis exists only as a trophozoite; no cyst stage has been identified.', 'role': 'assistant'}]