The correct answer is: a) Phosphate.
Phosphate is a mineral that is mined in the Panchmahal district for use in the fertilizer industry. It is a major component of fertilizer, and is also used in other industries such as the production of detergents and pharmaceuticals.
Gypsum is a mineral that is used in the construction industry, as well as in the production of plasterboard and drywall. It is also used in agriculture as a soil amendment.
Lignite is a type of coal that is used in the production of electricity. It is a lower-grade coal than bituminous coal or anthracite coal, and has a higher moisture content.
Bauxite is a mineral that is used in the production of aluminum. It is the most important ore of aluminum, and is found in a number of countries around the world.
In conclusion, the correct answer to the question “Which mineral is mined in the Panchmahal district for use in the fertilizer industry?” is: a) Phosphate.