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': 'Which of the following is a bacteria taxonomically -a) Chlamydiab) Rickettsiac) Mycoplasmad) Prione) Bacteriophage \nSelect and explain. \nA. ab, B. abc, C. acd, D. bcd', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Bacteria\n\nBacteria are single celled microorganisms which can exist either as independent (free living) organisms or as parasites (dependent on other organisms for life).\nThere are typically 40 million bacterial cells in a gram of soil and 1 million bacterial cells in a millilitre of fresh water; in all, there are approximately five nonillion (5 x 1030 ) bacteria on earth.', 'role': 'assistant'}]