Right choice is (d) NaOH, Na2S, Na2CO3 In aqueous solution
Explanation: 60%NaOH, 25% Na2 S, 15% Na2CO3 in 10-15%aqueous solution is the chemical reagent used in digestors of sulfate pulp process Mg(HSO3)2 + SO2, Na2CO3 + Na2S + NaHCO3, NaHSO3 + Na2 SO3 are the chemical reagents used in different types of sulfite processes.