This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'Giardiasis is best diagnosed by: \nSelect and explain. \nA. CFT, B. Presence of both cysts and trophozoites in stools, C. Presence of cysts only, D. Haemaglutination', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Presence of both cysts and trophozoites in stools', 'role': 'assistant'}]