The correct answer is a) Rock phosphate.
Rock phosphate is a mineral that is used in the fertilizer industry. It is a major source of phosphorus, which is an essential nutrient for plant growth. Rock phosphate is also used in the production of animal feed and in some industrial applications.
Gypsum is a mineral that is used in a variety of applications, including construction, agriculture, and industry. It is a major source of calcium and sulfur, which are essential nutrients for plant growth. Gypsum is also used in the production of drywall, plaster, and cement.
Nitrates are salts that are found in nature and are also produced industrially. They are used in fertilizers, explosives, and other applications. Nitrates are a major source of nitrogen, which is an essential nutrient for plant growth.
Potash is a mineral that is used in fertilizers, glassmaking, and other applications. It is a major source of potassium, which is an essential nutrient for plant growth. Potash is also used in the production of soap, detergents, and other products.
In conclusion, rock phosphate is the mineral that is crucial in the fertilizer industry. It is a major source of phosphorus, which is an essential nutrient for plant growth.