<prompt> Most common side effect of 5-Fluorouracil is-GI. toxicityBone marrow depressionCardiotoxicityNeurotoxicity  <response>: 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. 