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
Spinal pa of accessory nerve supplies 
Select and explain. 
A. Platysma, B. Sternocleidomastoid, C. Stylohyoid, D. Diagastric
B: Sternocleidomastoid
Answer: B: Sternocleidomastoid 
Explanation: 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 )