Here it is
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In this A is a carboxylic acid derivative which can be either acid halide, anhydride, ester or amide or  it can be a nitrile also. Hydrolysis of all above compounds which are carboxylic acid derivatives,  give carboxylic acid on addition of water in the presence of acid or base.
In carboxylic acid derivatives amides are the least reactive because they don't have any good leaving group on them.
So A can be either an ester or an anhydride or a acid halide. One mole of these derivatives, react with two moles of the Grignard reagent, the first mole  of Grignard reagent reacts with the compounds mentioned to form a ketone as an intermediate Reaction with 2nd mole of Grignard reagent forms a tertiary alcohol in which two of the alkyl groups are identical and have come from the Grignard reagent.
B is a tertiary alcohol with (CH₃)₂CH-C(OH)(CH₃)₂