ANS:A - graphite

1. Graphite:
   • Graphite is a form of carbon with a unique molecular structure that allows it to leave marks on paper when applied with pressure.
   • It is widely used in pencils due to its softness, ability to write smoothly, and its dark mark.
   • Graphite is not toxic like lead, making it a safe material for use in pencils.
2. Lead sulphide:
   • Lead sulfide (PbS) is a compound of lead and sulfur.
   • It is not typically used in pencils.
   • Lead sulfide is a dark, shiny material but not suitable for writing purposes like graphite.
3. Lead:
   • Historically, pencils were indeed made with a core of lead, but this usage of lead was phased out due to health concerns.
   • Lead is toxic and can cause lead poisoning if ingested or if particles are inhaled. This poses significant health risks, particularly for children.
   • The misconception that pencils contain lead likely arose from the historical use of lead in their manufacture, but modern pencils do not contain lead.
4. Both (b) & (c):
   • This option suggests that pencils contain both lead sulphide and lead, which is incorrect based on modern pencil manufacturing methods.
   • As mentioned earlier, graphite is the primary material used in pencils today, not lead or lead sulphide.