This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'Commonest trophozite infection by sexual intercourse - \nSelect and explain. \nA. Entamoeba histolytica, B. Trichomonas vaginalis, C. Trepanoma palidium, D. Giabrdia intestinales', 'role': 'user'}, {'content': "Answer: B \nExplanation: Trichomoniasis has an estimated annual incidence of 173 million cases(Ref.PARK'S TEXTBOOK OF PREVENTIVE AND SOCIAL MEDICINE 21st Edition page no.304)", 'role': 'assistant'}]