In which of the following can peroxide effect operate?

The reaction of propene with $\mathrm{HBr}$ in presence of peroxide proceeds through the intermediate

$3$-Phenylpropene reacts with $\mathrm{HBr}$ in the presence of peroxide, the major product formed

Observe the following reactions and predict the nature of $\mathrm{A}$ and $\mathrm{B}$ 

$\mathrm{B}\underset{\mathrm{hv}}{\overset{\mathrm{HBr}}{\leftarrow }}$  $\stackrel{\mathrm{HBr}}{\to }\mathrm{A}$