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': 'Which of the following type of fissure is not self cleansable? \nSelect and explain. \nA. I, B. IK, C. Inverted Y, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: MORPHOLOGY OF PIT & FISSURES\nNagano (1961) described following principal types of fissures, based on the alphabetical description of shape:\n\nV – Type (34%)\nU – Type (14%)\nI – Type (19%)\nIK – Type (26%)\nInverted Y – Type (7%)', 'role': 'assistant'}]