Reactions (a) and (b) indicate that both $\mathrm{AgNO_3}$ and $\mathrm{CuSO_4}$ oxidise $\mathrm{H_3PO_2}$ to $\mathrm{H_3PO_4}$. Hence, both are oxidising agents. Reactions (c) and (d) suggest that $\mathrm{[Ag(NH_3)_2]}^{+}$ oxidises $\mathrm{C_6H_5CHO}$ (benzaldehyde) to $\mathrm{C_6H_5COO}^{-}$ (benzoate ion) but $\mathrm{Cu}^{2+}$ ions cannot oxidise $\mathrm{C_6H_5CHO}$ to $\mathrm{C_6H_5COO}^{-}$. Therefore, from the above reactions, we infer that $\mathrm{Ag}^{+}$ ion is a stronger oxidising agent than $\mathrm{Cu}^{2+}$ ion.