Solution:
As you can see the image of rectangle L'M'N'O' is smaller in size than preimage LMNO.
As in dilation pre image and image are similar. But rectangle LMNO and L'M'N'O' are not similar, So Dilation is not possible.
Yes, Rectangle LMNO is stretched or shrinked to get rectangle L'M'N'O'.
In reflection and rotation both preimage and image are congruent.
So, only option (2) i.e Stretch looks correct.