The correct answer is $\boxed{\text{B}}$, Ca(OH)2. Quicklime is a chemical compound with the formula CaO. It is a white, caustic, alkaline, crystalline solid that is produced by heating limestone (calcium carbonate) to a high temperature. Quicklime is used in a variety of industrial processes, including the production of cement, lime mortar, and plaster. It is also used in agriculture as a liming agent to improve soil pH.
Option $\text{A}$, CaCO3, is the formula for limestone. Limestone is a sedimentary rock composed primarily of calcium carbonate. It is a common rock type that is found in many parts of the world. Limestone is used in a variety of industries, including the construction industry, the chemical industry, and the fertilizer industry.
Option $\text{C}$, CO3CO2, is the formula for carbonic acid. Carbonic acid is a weak acid that is formed when carbon dioxide dissolves in water. It is found in many natural sources, including carbonated beverages and rainwater. Carbonic acid is also used in a variety of industrial processes, including the production of soda ash and the manufacture of steel.
Option $\text{D}$ is incorrect.