Explanation:

- Option 1: Limestone

- Limestone is a sedimentary rock mainly composed of calcium carbonate.

- It’s used to produce cement and lime but not Plaster of Paris.

- Option 2: Silica

- Silica is a hard, unreactive, colorless compound often found in quartz.

- It's a major component in glass and sand but not in making Plaster of Paris.

- Option 3: Bauxite

- Bauxite is the principal ore of aluminum.

- It’s used to create aluminum products but has no role in making Plaster of Paris.

- Option 4: Gypsum

- Plaster of Paris is created by heating gypsum to about 150°C.

- It results in a white powder that hardens upon adding water.

- Correct Answer: Gypsum

- Gypsum undergoes calcination to form Plaster of Paris efficiently.