To solve this problem, we need to match the compounds in List-I with their corresponding reactants in List-II.$\newline$Let's analyze each pair:$\newline \newline$(a) Cyanohydrin:$\newline$• Cyanohydrins are formed by the reaction of aldehydes or ketones with hydrogen cyanide (HCN).$\newline$• Therefore, the correct match is (a) \rightarrow (iv).$\newline \newline$(b) Acetal:$\newline$• Acetals are formed by the reaction of aldehydes or ketones with alcohols.$\newline$• Therefore, the correct match is (b) \rightarrow (iii).$\newline \newline$(c) Schiff’s Base:$\newline$• Schiff's bases are formed by the reaction of aldehydes or ketones with primary amines (RNH_2).$\newline$• Therefore, the correct match is (c) \rightarrow (ii).$\newline \newline$(d) Oxime:$\newline$• Oximes are formed by the reaction of aldehydes or ketones with hydroxylamine (NH_2OH).$\newline$• Therefore, the correct match is (d) \rightarrow (i).$\newline \newline$Based on the analysis above, the correct option is:$\newline$Option 4: (a) \rightarrow (iv), (b) \rightarrow (iii), (c) \rightarrow (ii), (d) \rightarrow (i).