Answer:
Looks like the scale factor is 1/3.
Step-by-step explanation:
(In this dilation, the green image is polygon ABCDE, and the red image is polygon A'B'C'D'E'. The red image is the resulting image after said dilation.)
A scale factor greater than one enlarges an image, and a scale factor between zero and one shrinks an image, so that rules out options 2 (SF = -3) and 3 (SF = 3).
A negative scale factor would end up in an image opposite the center of enlargement, so that eliminates option 4 (SF = -1/3).
So that means that the scale factor is option 1 (SF = 1/3)!
