Langbeinite process is associated with manufacturing of which fertilizer?

Answer: Option C

Langbeinite process is associated with the manufacturing of K₂SO₄ (Potassium Sulphate) fertilize.
Langbeinite is a potassium magnesium sulfate mineral with the chemical formula K₂Mg₂(SO₄)₃. Langbeinite crystallizes in the isometric-tetartoidal (cubic) system as transparent colorless or white with pale tints of yellow to green and violet crystalline masses.
Langbeinite is treated with a concentrated solution of potassium chloride to yield precipitates of potassium sulfate. The precipitates of potassium sulphate are separated from the solution by decantation.