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: Dental
[{'content': 'Tanerella forsythus is a periodontal pathogen \nSelect and explain. \nA. Gram positive, non-obligate, B. Non-pleomorphic rod, C. Non - obligate anaerobe, D. Non-motile, spindle shaped organism', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]