The correct answer is: Cement.
Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO3). It is the most common sedimentary rock on Earth, and it is found in a variety of colors, including white, gray, brown, and black. Limestone is formed when the remains of marine organisms, such as coral and shellfish, are buried and compacted over time.
Cement is a binding agent that is used to hold together other materials, such as sand and gravel, to form concrete. Concrete is one of the most widely used building materials in the world, and it is used in a variety of structures, including buildings, bridges, and roads.
Limestone is a major source of calcium carbonate, which is the main ingredient in cement. The limestone deposits in Manipur are significant for the production of cement. The limestone is quarried and then crushed into small pieces. The crushed limestone is then heated in a kiln to remove the water and carbon dioxide. The resulting product is called clinker. Clinker is then ground into a powder and mixed with gypsum to form cement.
The production of cement is a major industry in Manipur. The cement industry employs thousands of people and contributes significantly to the state’s economy.
The other options are incorrect because:
- Fertilizer is made from a variety of materials, including phosphate rock, potash, and nitrogen. Limestone is not a major source of any of these materials.
- Pharmaceuticals are made from a variety of materials, including plants, animals, and minerals. Limestone is not a major source of any of these materials.
- Construction materials are made from a variety of materials, including wood, steel, and concrete. Limestone is a major source of concrete, but it is not the only material that can be used to make construction materials.