Which of the following is the most suitable method to remove trace amounts of water from ethanol?

When a Grignard reagent reacts with $(B)$,product $(D)$ is obtained. Reactant $(A)$ of the above reaction is:
$(A)$ $\xrightarrow{PBr_3} (C)$ $\xrightarrow{Mg, \text{ether}} \text{Grignard reagent}$
$(A) \xrightarrow{Na_2Cr_2O_7, H_2SO_4} (B)$
$\text{Grignard reagent} + (B) \to (D) \xrightarrow{H_3O^\oplus} (3,4-\text{dimethylhexan-3-ol})$

The boiling point of glycerol is higher than that of propanal because of:

$A$ sample of $4.5 \ g$ of an unknown monohydric alcohol,$ROH$,was added to methylmagnesium iodide. $A$ gas is evolved,collected,and its volume is measured to be $3.1 \ L$ at $NTP$. The molecular weight of the unknown alcohol is $g/mol$. [Nearest integer]

Glycerol is used in the manufacture of

Isopropyl alcohol on oxidation gives