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
The drug imatinib acts by the inhibition of : 
Select and explain. 
A. Tyrosine kinase, B. Glutathione reductase, C. Thymidylate synthetase, D. Protein kinase
A: Tyrosine kinase
Answer: A: Tyrosine kinase 
Explanation: None