The condition for a uniform spherical mass `m` of a radius `r` to be a black hole is [`G` =gravitational constant and `g`=acceleration due to gravity]
A. `(2Gm//r)^(1//2) lt c`
B. `(2Gm//r)^(1//2) = c`
C. `(2Gm//r)^(1//2) ge c`
D. `(gm//r)^(1//2) ge c`