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: Anatomy
[{'content': 'In elevation of the eyebrows and production of transverse wrinkles of the face: \nSelect and explain. \nA. Only the occipital bellies of occipitofrontalis act, B. Only the frontal bellies of occipitofrontalis act, C. Both the bellies act simultaneously, D. Both the bellies act one after the other', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Occipitofrontalis muscle consists of two parts or bellies; the occipital belly is near the occipital bone,\xa0and the frontal belly near the frontal bone of the forehead.\n\nFlat digastrics muscle with occipital and frontal bellies share a common tendon (epicranial\xa0aponeurosis).\nIndependently the occipital belly retracts the scalp, frontal belly protracts the scalp.\nSimultaneously they elevate eyebrows, produce wrinkles across the forehead, surprised look.\n\n\u200bKey Concept:\n\nThe frontal bellies are longer, wider and partly united in the median plane. Each arises from the skin of the upper eyelid and forehead, mingling with the orbicularis oculi and the corrugator supercilii. It is supplied by the temporal branch of the facial nerve.\nThe muscle raises the eyebrows and causes horizontal wrinkles in the skin of the forehead.', 'role': 'assistant'}]