The correct answer is: a) Limestone.
Limestone is a sedimentary rock composed mostly of calcium carbonate (CaCO3). It is the most common sedimentary rock on Earth, and the most widely used industrial mineral. Limestone is used in the manufacture of cement, lime, and other building materials, as well as in the production of iron and steel, glass, and paper.
Coal is a fossil fuel formed from the remains of ancient plants that have been buried and subjected to intense heat and pressure over millions of years. It is a solid, black or brown, combustible material that is used as a fuel for generating electricity, heating homes and businesses, and powering vehicles.
Iron ore is a mineral that contains iron. It is the primary raw material used in the production of iron and steel. Iron ore is found in rocks and minerals all over the world, but the most important deposits are located in China, Australia, Brazil, and Russia.
Copper is a chemical element with the symbol Cu and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. Copper is one of the most widely used metals in the world, and is a major component of many electrical and electronic devices.