Given the points:
[tex]\begin{gathered} B\colon(-3,-1) \\ C\colon(-3,3) \\ D\colon(0,3) \end{gathered}[/tex]We need to reflect the points over the line y = x
The rule of reflection is as follows:
[tex](x,y)\rightarrow(y,x)[/tex]So, the points after reflection will be:
[tex]\begin{gathered} B^{\prime}\colon(-1,-3) \\ C^{\prime}\colon(3,-3) \\ D^{\prime}\colon(3,0) \end{gathered}[/tex]