Identify the product $B$ in the following reaction.
Dry ice $\xrightarrow[\text{dry ether}]{CH_3MgBr} A$ $\xrightarrow{H_3O^{+}} B$

Identify product $C$ in the following conversion sequence: $m$-Hydroxybenzaldehyde $\xrightarrow[\text{Protection of } -OH \text{ group}]{C_6H_5CH_2Cl} A$ $\xrightarrow{[O]} B$ $\xrightarrow{\text{deprotection}} C$.

The major product in the following reaction is:

Which of the following acids cannot be prepared by a Grignard reagent?

What is obtained when glycerol is heated with oxalic acid at $110\,^{\circ}C$?

Which among the following compounds is $NOT$ used for the preparation of aromatic carboxylic acids from alkyl benzene?