The correct order of heat of combustion for following alkadienes is:

The major product of the following reaction is

The major product of the following reaction is :

The major product formed in the following reaction is :

${\mathrm{CH}}_3\mathrm{CH}=\mathrm{CHCH}{\left({\mathrm{CH}}_3\right)}_2\stackrel{\mathrm{HBr}}{\to }$

In the following reaction sequence the major products $\mathrm{A}$ and $\mathrm{B}$ are :