This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Upper limb, Subject name: Anatomy
[{'content': 'Spinal pa of accessory nerve supplies \nSelect and explain. \nA. Platysma, B. Sternocleidomastoid, C. Stylohyoid, D. Diagastric', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Sternocleidomastoid and trapezius are supplied by spinal accessory nerve. Both of them develop from brachial arch mesoderm.It is tested by turning the neck against resistance.B D Chaurasia 7th edition Page no: 65 ( refer head and neck volume )', 'role': 'assistant'}]