Answer:
2/3
Step-by-step explanation:
You can't have a negative scale factor, so you can automatically eliminate options A and B. A scale factor is simply a number that can be multiplied by an original side to get a new side (a number larger than 1 means it's getting bigger)
Contraction is when a dilation gets smaller, so 2/3 is the only option which is smaller than 1, but also not negative.