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: Dental
[{'content': 'All are true about Experimental trials except: \nSelect and explain. \nA. Can’t double blind in animal trials, B. All animal trials are unethical, C. Can’t do interim analysis, D. Are always prospective', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]