The correct answer is D. k= 3
Explain
First , point ( x,y) by factor k
It will become (x/k,y)
The vertex is (-3,-3) of f(x)
And the other vertex is (-1,-3) of g(x)
-1,-3)= (-3/3 ,3)
So the dilation factor is 3
(-1,-3) = (-3 x 1/3 ,3)
Factor is k
g(x)= f(1/3 x)
So k = 3
Because the graph have shrunk f(x) by factor 3
I Hope this make sense to you
Glad I can help you :D