Q. Which of the following is an ore of lead?
Answer: Galena
Notes: Galena (PbS) is the most important lead ore. It contains lead sulfide as the primary metal. Magnesite is magnesium carbonate and not a lead ore. Phosphorite is a phosphate rock used for phosphorus fertilizers. Graphite is a form of carbon used in pencils and electrodes, not for lead extraction.