Given below are two statements.

Statement I: Two different aldehydes on cross aldol condensation always give four products.

Statement II: Among benzaldehyde and acetophenone, only acetophenone reacts with semicarbazide.

Choose the correct option.

The correct option is: Both statement I and statement II are incorrect.

Analysis of Statement I:
Aldol condensation requires the formation of a carbanion/enolate intermediate, which is generated by removing an α-hydrogen from a carbonyl compound. when two different aldehydes undergo cross aldol condensation, they will yield four different products (two self-condensation and two cross-condensation products) only if both aldehydes possess α-hydrogens.
If one of the aldehydes lacks α-hydrogens (such as formaldehyde, HCHO, or benzaldehyde, C₆H₅CHO), it cannot form a nucleophilic enolate ion. Consequently, it cannot undergo self-condensation, and the reaction typically yields only two products (one self-condensation product and one cross-condensation product). Therefore, two different aldehydes do not always give four products, making Statement I incorrect.

Analysis of Statement II:
Semicarbazide (H₂N-NH-CO-NH₂) is a nucleophilic reagent that reacts with carbonyl compounds (both aldehydes and ketones) via nucleophilic addition followed by the elimination of a water molecule to produce crystalline derivatives called semicarbazones.
Since benzaldehyde (an aldehyde) and acetophenone (a ketone) both contain a reactive carbonyl group (C=O), both of them readily react with semicarbazide. Thus, the assertion that only acetophenone reacts with semicarbazide is incorrect, making Statement II incorrect.