Refer to the below equation :

The products are

$\begin{array}{1 1}a)\;constitutional \;isomers\\b)\;diastereomers\\c)\;enantiomers\\d)\;Geometrical \;isomers\end{array}$

The addition to double bond can take place in two ways one above the plane and another below the plane so that a mixture of diastereomers results are of
Hence (b) is the correct answer.