Q. Which of the following is a redox reaction?
A \(\mathrm{NaCl}+\mathrm{KNO}_{3} \longrightarrow \mathrm{NaNO}_{3}+\mathrm{KCl}\)
B \(\mathrm{CaC}_{2} \mathrm{O}_{4}+2 \mathrm{HCl} \longrightarrow \mathrm{CaCl}_{2}+\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\)
c \(\mathrm{Mg}(\mathrm{OH})_{2}+2 \mathrm{NH}_{4} \mathrm{Cl} \longrightarrow \mathrm{MgCl}_{2}+2 \mathrm{NH}_{4} \mathrm{OH}\)
(D) \(\mathrm{Zn}+2 \mathrm{AgCN} \longrightarrow 2 \mathrm{Ag}+\mathrm{Zn}(\mathrm{CN})_{2}\).