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: Pharmacology
[{'content': 'The drug imatinib acts by the inhibition of : \nSelect and explain. \nA. Tyrosine kinase, B. Glutathione reductase, C. Thymidylate synthetase, D. Protein kinase', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]