Answer:
None is
Explanation:
Given
Volume and Surface area of a cube
Required
Which is linear
The volume of a cube is:

While the surface are is:

Where x represents the length of the side
A linear function construct is represented as:

By comparing A(x) and V(x) to f(x):
f(x) do not have any form of exponent while A(x) and V(x) have.
So, we can see that both functions are not linear