<prompt> Most common side effect of 5-fluorouracil is:G.I. toxicityBone marrow depressionCardiotoxicityNeeurotoxicity  <response>: Ref: KDT 6e p824; Harrison 16e p596 Diarrhea is the most common adverse effect of 5-FU. It can also cause hand and foot syndrome and bone marrow suppression. 