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': 'In root end preparation: \nSelect and explain. \nA. Tunnel type cavity is prepared, B. Class I cavity is prepared, C. Vertical slot is prepared, D. Any of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Car and Bentkover defined an ideal root-end preparation as "A\xa0class\xa0I preparation at least 3.0 mm into root dentine with walls parallel to a\xa0coincident with the anatomic outline of the pulp space".\nFive requirements suggested for a root end preparation to fulfill:\n\nThe apical 3 mm of root canal must be freshly cleaned and\xa0shaped.\nPreparation must be parallel to the anatomic outline of the pulp cavity.\nCreation of an adequate retention form.\nRemoval of all isthmus tissue if present.\nRemaining dentin\xa0walls should not be weakened.\n\nTextbook of Endodontics Nisha Garg 3rd Ed', 'role': 'assistant'}]