1. Principle for nucleophilic addition to carbonyl compounds

   The reactivity of aldehydes and ketones toward nucleophilic addition depends mainly on:

   • Electronic effect: More positive carbonyl carbon means more reactive.
   • Steric hindrance: Less crowding around the carbonyl carbon means easier attack.

2. General order: aldehydes vs ketones

   Aldehydes are generally more reactive than ketones because:

   • They have only one alkyl group (or one H), so there is less +I effect.
   • They are less sterically hindered.

   Hence, $\text{aldehydes} > \text{ketones}$

3. Compare the two ketones: propanone vs butanone

   • Propanone: $CH_3COCH_3$
   • Butanone: $CH_3COC_2H_5$

   The ethyl group in butanone has greater electron-donating effect and also causes more steric hindrance than a methyl group.

   Therefore, $\text{Butanone} < \text{Propanone}$

4. Compare the two aldehydes: propanal vs benzaldehyde

   • Propanal: $CH_3CH_2CHO$
   • Benzaldehyde: $C_6H_5CHO$

   In benzaldehyde, the carbonyl group is conjugated with the benzene ring. Due to resonance, the positive character on the carbonyl carbon decreases, so nucleophilic addition becomes less favorable than in aliphatic aldehydes.

   Thus, $\text{Benzaldehyde} < \text{Propanal}$

5. Combine all comparisons

   From above: $\text{Butanone} < \text{Propanone} < \text{Benzaldehyde} < \text{Propanal}$

6. Match with options

   This matches Option A.

Final Answer: $\boxed{\text{Butanone} < \text{Propanone} < \text{Benzaldehyde} < \text{Propanal}}$