This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head and neck, Subject name: Anatomy
[{'content': 'Deep injury of neck always involves \nSelect and explain. \nA. Platysma, B. Trapezius, C. Sternocleidomastoid, D. Longus colli', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Investing layer lies deep to the platysma and surrounds the neck like a collar. The surgeon has to stitch platysma muscle separately so that skin does not adhere to deeper neck muscles otherwise the skin will get an ugly scar. Ref BDC volume 3;sixth edition pg 81', 'role': 'assistant'}]