Given:
The image of polygon MNOP after a similarity transformation is WXYZ.
Each side of MNOP is 2 times as long as the corresponding side of WXYZ.
To find:
The scale factor of the dilation in the similarity transformation.
Solution:
We know that, the scale factor is

We know that, MNOP is the original figure and WXYZ is the image. MN is corresponding side of WX.
...(i)
Each side of MNOP is 2 times as long as the corresponding side of WXYZ.

...(ii)
From (i) and (ii), we get

Therefore, the correct option is B.