The change in the value of `g` at a height `h` above the surface of the earth is the same as at a depth d below the surface of earth. When both `d` and `h` are much smaller than the radius of earth, then which one of the following is correct?
A. `x=h`
B. `x=2h`
C. `x=h/2`
D. `x=h^(2)`
