Answer=C
The formula for the volume of a rectangular prism is
V=l*w*h where l=length w=width and h=height
So lets double each of the dimensions and see what it does to the volume
V=2l*2w*2h
V=8*l*w*h
So when you double each of the dimensions, the volume becomes 8 times greater, which isn't an option. Did you correctly write the question?
For example if the dimensions for l,w & h are 2
V=2*2*2=8
but if they are doubled
V=4*4*4=64
64/8=8
So it's 8 times greater...