The correct answer is (c) Graphite.
Lead pencils do not contain lead. They contain graphite, which is a form of carbon. Graphite is a soft, black material that is used in pencils because it can be easily rubbed off onto paper. Lead oxide is a compound of lead and oxygen. It is a white, powdery substance that is used in some paints and ceramics. Lead sulfide is a compound of lead and sulfur. It is a black, crystalline substance that is used in some batteries and pigments.
Lead pencils were originally made with lead, but this was found to be dangerous because lead is a toxic metal. Graphite is a much safer alternative, and it also produces a darker line than lead.