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': "In anterior mandibular occlusal projection, the central X-ray beam enters the patient's face through the: \nSelect and explain. \nA. Tip of the chin, B. Tip of the nose, C. Floor of the mouth, D. Below the chin", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Anterior mandibular occlusal projection\nReceptor Placement:\xa0Seat the patient tilted back so that the occlusal plane is 45 degrees above horizontal. Place the receptor in the mouth with the long axis perpendicular to the sagittal plane and push it posteriorly until it touches the rami. Center the receptor with the pebbled side (tube side) down, and ask the patient to bite lightly to hold the receptor in position.\nProjection of Central Ray:\xa0Orient the central ray with −10 degrees angulation through the point of the chin toward the middle of the receptor; this gives the ray −55 degrees of angulation to the plane of the receptor.\nPoint of Entry:\xa0The point of entry of the central ray is in the midline and through the tip of the chin.', 'role': 'assistant'}]