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: Pharmacology
Most common side effect of 5-fluorouracil is: 
Select and explain. 
A. G.I. toxicity, B. Bone marrow depression, C. Cardiotoxicity, D. Neeurotoxicity
A: G.I. toxicity
Answer: A: G.I. toxicity 
Explanation: (Ref: KDT 6/e p824; Harrison 16/e p596) Diarrhea is the most common adverse effect of 5-FU. It can also cause hand and foot syndrome and bone marrow suppression.