foolproof

adj. 错不了的，容易懂的

fondant, fondle, fondly, fondness, fondue, font, food, food processor, food value, food-chain, foodstuff, fool, fool around, fool with, foolery, foolhardiness, foolhardy, foolish, foolishly, foolishness, foolscap, foot, foot-and-mouth, foot-and-mouth (disease), foot-bridge, foot-fault, foot-note, foot-slog, footage, football, football pitch, footbrake, footfall, foothill, foothold, footing, footle, footlight, footlights, footling,