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: Physiology
[{'content': 'The main types of muscle cells are \nSelect and explain. \nA. Skeletal and cardiac, B. Smooth and cardiac, C. Smooth and skeletal, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]