This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
[{'content': 'Upon contact between the sperm head and the zona pellucida, penetration of the sperm into the egg is allowed because of \nSelect and explain. \nA. The acrosome reaction, B. The zona reaction, C. The perivitelline space, D. Pronuclei formation', 'role': 'user'}, {'content': 'Answer: A \nExplanation: .', 'role': 'assistant'}]