Which one of the following will most readily be dehydrated in acidic condition?

The major product formed in the following reaction is:

Identify compound $A$ from the following reaction:
$A + C_2H_5MgBr$ $\xrightarrow[ether]{dry} B$ $\xrightarrow{H_3O^{+}} 3-\text{methylpentan}-3-\text{ol}$

$HCHO$ (more reactive towards oxidation) + $CH_3CHO \xrightarrow{Conc. NaOH}$ Find out the products of the reaction.

An ester $(A)$ with molecular formula $C_9H_{10}O_2$ was treated with excess of $CH_3MgBr$ and the complex so formed was treated with $H_2SO_4$ to give an olefin $(B)$. Ozonolysis of $(B)$ gave a ketone with molecular formula $C_8H_8O$ which shows positive iodoform test. The structure of $(A)$ is

Given below are two statements:
Statement $I$ : Acidity of $\alpha$-hydrogens of aldehydes and ketones is responsible for Aldol reaction.
Statement $II$ : Reaction between benzaldehyde and ethanal will $NOT$ give Cross-$Aldol$ product.
In the light of above statements,choose the most appropriate answer from the options given below.