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
Most common side effect of 5-Fluorouracil is- 
Select and explain. 
A. GI. toxicity, B. Bone marrow depression, C. Cardiotoxicity, D. Neurotoxicity
A: GI. toxicity
Answer: A: GI. toxicity 
Explanation: Ans. is 'a' i.e., GI toxicity o The earliest untoward symptoms during a course of 5-FU are anorexia and nausea; these are followed by stomatitis and diarrhea.