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': 'Muscle attached to the tubercle of 1st cervical vertebrae \nSelect and explain. \nA. Scalenus anterior, B. Scalenus medium, C. Scalenus minimum, D. Scalenus posterior', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]