d
When alkenes are treated with \(HBr\) in the presence of peroxides, an anti-Markovnikov addition occurs in the sense that the hydrogen atom becomes attached to the carbon atom with the fewer hydrogen atoms.

The product formed has two chirality centres, therefore, four stereoisomers \(\left(2^{2}\right)\) will exist.

\(\begin{array}{*{20}{c}}
  {\,\,\,\,\,C{H_3}} \\ 
  | \\ 
  {C{H_3} - C{H_2} - C = CH - C{H_3}} 
\end{array}\) \(\xrightarrow[{Peroxide}]{{HBr}}\) \(\mathop {\begin{array}{*{20}{c}}
  {\,\begin{array}{*{20}{c}}
  {\,\,\,\,\,\,C{H_3}} \\ 
  | 
\end{array}} \\ 
  {C{H_3} - C{H_2} - {}_*CH - \mathop {CH}\limits^{*\,}  - C{H_3}} \\ 
  {\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|} \\ 
  {\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,Br} 
\end{array}}\limits_{Major\,\,product} \)