This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Other topics and Adverse effects, Subject name: Anatomy
The mechanism of anti cancer action of fluoruracil is 
Select and explain. 
A. Cross linking of double standard DNA and the resulting inhibition of DNA replication and transcription, B. Cytotoxicity resulting from metabolite that interferes with the production of dTMP, C. Irreversible inhibition of dihydrofolic acid reductase, D. Selective action of DNA polymerase
C: Irreversible inhibition of dihydrofolic acid reductase
Answer: C: Irreversible inhibition of dihydrofolic acid reductase 
Explanation: 5-FU is an antimetabolite.it us a thymidine analogue and acts by conversion to 5'-dUMP .latter inhibits the formation of dTMP and result in Thymineless dealth of cells Ref-KDT 6/824