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: Medicine
[{'content': 'Normal hea axis is: \nSelect and explain. \nA. -90 to + 90deg, B. -90 to + 180deg, C. -30 to +90deg, D. -90 to 180deg', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Answer is C (-30 to +90deg)', 'role': 'assistant'}]