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: Unknown
[{'content': 'Comment on this CTG \nSelect and explain. \nA. Normal, B. Early deceleration, C. Late deceleration, D. Variable deceleration', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]