Superphosphate of lime—a phosphate fertilizer—is obtained by the reaction of

Superphosphate of lime is a widely used phosphate fertilizer manufactured by treating insoluble calcium phosphate (rock phosphate) with concentrated sulphuric acid. The reaction is: Ca3(PO4)2 + 2H2SO4 → Ca(H2PO4)2 + 2CaSO4. The product is a mixture of monocalcium phosphate (soluble, plant-available) and calcium sulphate (gypsum). Sodium hydroxide, HCl, or nitric acid are not used in commercial superphosphate manufacture. Nitric acid is used to make nitrophosphate fertilizers, which are different products. Hence option (b) is correct.