Dehydration by conc. ${\mathrm{H}}_2{\mathrm{SO}}_4$ is the most difficult in

$\mathrm{A}$ & $\mathrm{B}$ are respectively

The most suitable reagent for given conversion is

In above reaction product $\left(\mathrm{B}\right)$ is

In above reaction product $\left(\mathrm{C}\right)$ is

Consider the following two structures

Choose the correct statement

Product $\left(\mathrm{C}\right)$ is