This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nucleotides, Subject name: Biochemistry
Inhibition of which of the following enzyme is responsible for the anticancer action of 5-Fluorouracil ? 
Select and explain. 
A. Dihydrofolate reductase, B. Thymidylate kinase, C. Thymidylate reductase, D. Thymidylate synthase
D: Thymidylate synthase
Answer: D: Thymidylate synthase 
Explanation: Drugs Inhibitor of 5-Fluorouracil thymidylate synthase(Suicidal inhibition) Methotrexate Dihydrofolate reductase Acyclovir thymidylate kinase