If the domain of the function, f, is restricted to x ≥ 0, which function is the inverse of f?

f(x)=9x^2 - 12 . x≥0

A.h(x)= sqrt-12/3

B.g(x)=sqrt x+12/3

C.g(x)=sqrtx+12/9

D.p(x)=sqrt x-12/9