Identify the correct set of aprotic solvent:

The reaction,

is fastest when $\mathrm{X}$ is:

The correct nucleophilicity order is:

Arrange the following alcohols for decreasing rate of reaction with concentrated ${\mathrm{H}}_2{\mathrm{SO}}_4$ at $180°\mathrm{C}$.

The major product formed in the reaction is

Compounds $A \& C$ in the following reaction are _____________

${\mathrm{CH}}_3\mathrm{CHO}\frac{\left(\mathrm{i}\right){\mathrm{CH}}_3\mathrm{MgBr}}{\left(\mathrm{ii}\right){\mathrm{H}}_2\mathrm{O}}\left(\mathrm{A}\right)\stackrel{{\mathrm{H}}_2{\mathrm{SO}}_4}{⟶}\left(\mathrm{B}\right)\stackrel{\text{Hydroboration oxidation }}{⟶}\left(\mathrm{C}\right)$

What is the relationship between the following compounds?