Which of the following aldehydes is most reactive towards nucleophilic addition reactions?

Benzene carbaldehyde (benzaldehyde) is reacted with concentrated $NaOH$ solution to give the products $A$ and $B$. The product $A$ can be used as a food preservative and the product $B$ is an aromatic hydroxy compound where the $OH$ group is linked to an $sp^3$ hybridized carbon atom next to the benzene ring. The products $A$ and $B$ are respectively,

Which of the following on reaction with Grignard reagent followed by hydrolysis forms a secondary alcohol?

The product $(A)$ of the following reaction is:

$CH_3-CO-CH_3$ $\xrightarrow{I_2/NaOH} \underset{\text{yellow compound}}{(A)} + (B)$ $\xrightarrow{Ag - \text{powder}, \Delta} (C)$ $\xrightarrow{Dil. H_2SO_4/HgSO_4} (D)$
$A, C$ and $D$ are :-

Oxidation of ketones involves carbon-carbon bond cleavage. Name the products formed on the oxidation of $2,5-$dimethylhexan$-3-$one.