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': 'Anesthetic testing is most effective in  localizing pain \nSelect and explain. \nA. to a specific tooth., B. to the mandible or maxilla., C. across the midline of  the face., D. to a posterior tooth.', 'role': 'user'}, {'content': "Answer: B \nExplanation: Selective Anesthesia\nWhen\xa0 symptoms\xa0 are\xa0 not\xa0 localized\xa0 or\xa0 referred,\xa0 the\xa0 diagnosis may be challenging. Sometimes the patient may not even be able to specify whether the symptoms are emanating from the maxillary or mandibular arch. In these instances, when pulp testing is inconclusive, selective anesthesia may be helpful.If\xa0 the\xa0 patient\xa0 cannot\xa0 determine\xa0 which\xa0 arch\xa0 the\xa0 pain\xa0 is coming from, then the clinician should first selectively anesthetize\xa0 the\xa0 maxillary\xa0 arch.\xa0 This\xa0 should\xa0 be\xa0 accomplished\xa0 by using a periodontal ligament (intraligamentary) injection. The injection\xa0 is\xa0 administered\xa0 to\xa0 the\xa0 most\xa0 posterior\xa0 tooth\xa0 in\xa0 the quadrant\xa0 of\xa0 the\xa0 arch\xa0 that\xa0 may\xa0 be\xa0 suspected,\xa0 starting\xa0 from\xa0 the distal sulcus. The anesthesia is subsequently administered in an anterior direction, one tooth at a time, until the pain is eliminated. If the pain is not eliminated after an appropriate period of time, then the clinician should similarly repeat this technique on the mandibular teeth below. It should be under-stood that periodontal ligament injections may anesthetize an adjacent tooth and thus are more useful for identifying the arch rather than the specific tooth.\nCohen's Pathway of the Pulp ed:11th Pg20", 'role': 'assistant'}]