ANS:B - sulphuric acid

Superphosphate is manufactured by reacting phosphate rock with sulphuric acid. During the manufacturing process of superphosphate, phosphate rock, which is primarily composed of calcium phosphate, is treated with sulphuric acid. This reaction results in the formation of water-soluble phosphate compounds, mainly monocalcium phosphate [(Ca(H2PO4)2)], along with gypsum (calcium sulfate) as a by-product. The reaction can be represented as follows: Ca3(PO4)2+2H2SO4→Ca(H2PO4)2+2CaSO4Ca3​(PO4​)2​+2H2​SO4​→Ca(H2​PO4​)2​+2CaSO4​ The resulting product, monocalcium phosphate, is water-soluble and readily available for plant uptake, making superphosphate a valuable fertilizer for providing phosphorus to plants.