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': 'Saturated salt solution concentrates eggs of all, except - \nSelect and explain. \nA. Unfertilized egg of ascaris, B. Trichuris, C. Hymenolepis nana, D. Echinococcus granulosus', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]