Question : Limestone, chalk and marble are different forms of ____________.
Option 1: calcium carbonate
Option 2: sodium carbonate
Option 3: potassium carbonate
Option 4: magnesium carbonate
Correct Answer: calcium carbonate
Solution : The correct answer is calcium carbonate.
Calcium carbonate (CaCO 3 ) is the chemical that makes up chalk, marble, and limestone. Sedimentary rocks with an organic composition include limestone and chalk. The hard shells of extinct animals, such as corals and shellfish, have been left behind after their fleshy sections have broken down, forming these rocks. They belong to the calcareous group.