1. Cyanohydrin: Produced by the reaction of aldehydes or ketones with Hydrogen Cyanide ($HCN$). Thus, (a) matches with (IV).
2. Acetal: Formed by the reaction of aldehydes with Alcohols ($ROH$) in the presence of dry $HCl$ gas. Thus, (b) matches with (III).
3. Schiff's base: Substituted imines, known as Schiff's bases, are formed by the reaction of aldehydes or ketones with primary amines ($RNH_2$). Thus, (c) matches with (II).
4. Oxime: Formed by the reaction of aldehydes or ketones with Hydroxylamine ($NH_2OH$). Thus, (d) matches with (I).

Therefore, the correct matching is (a)-(IV), (b)-(III), (c)-(II), (d)-(I).