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: Radiology
[{'content': 'Root canal anatomy and variation will be best known when one takes \nSelect and explain. \nA. IOPA X-ray, B. IOPA with mesial angulation, C. IOPA mesial and distal angulation, D. Bitewing X-ray', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Often a single radiograph of a multirooted tooth made at the normal vertical and horizontal projection does not display all the\xa0roots. In these cases, when it is necessary to separate the roots on multirooted teeth, a second projection may be made.\nThe horizontal angulation is altered,\n\n20 degrees mesially for maxillary premolars.\n20\xa0degrees\xa0mesially\xa0or\xa0distally\xa0for\xa0maxillary\xa0molars.\n20\xa0degrees\xa0distally\xa0for\xa0an\xa0oblique\xa0projection\xa0of\xa0mandibular\xa0molar roots.\n\nRef: ORAL RADIOLOGY Principles\xa0and\xa0Interpretation,Stuart C. White,Michael J. Pharoah Edition 7 page no 129', 'role': 'assistant'}]