Answer:
c 1/2
Step-by-step explanation:
You are incorrect.
We are going from ABCDEFGH to A'B'C'D'E'F'G'H'. We are going from the large octagon to the small octagon. The scale factor of a dilation is the number you multiply the original lengths to get the lengths of the dilation.

Look at point (6, 0) which becomes (3, 0) in the dilation.
The distance from the origin to (6, 0) is 6 units.
The distance from the origin to (3, 0) is 3 units.
scale factor = dilated/original = 3/6 = 1/2
The scale factor of the dilation is 1/2.
Also look at segment AB whose length is 4. The length of segment A'B' is 2.
scale factor = dilated/original = 2/4 = 1/2
Answer: 1/2