Sully means to tarnish, defile, or damage something's purity or reputation - literally to make it dirty or figuratively to stain character. Besmirch (B) is a direct synonym meaning to soil, tarnish, or disgrace. Foppish (A) means fashionable in a pretentious way, Dulcet (C) means sweet or pleasant (sound/taste), and Dissipate (D) means to scatter or disperse - none relate to staining or damaging reputation.