If `epsilon_0` and `mu_0` are respectively the electric permittivity and the magnetic permeability of free space and `epsilon` and `mu` the corresponding quantities in a medium, the refractive index of the medium is
A. `sqrt((epsilon_(0)mu_(0))/(epsilon mu))`
B. `sqrt((epsilon mu)/(epsilon_(0)mu_(0)))`
C. `sqrt((epsilon_(0)mu)/(epsilon mu_(0)))`
D. `sqrt((epsilon)/(epsilon_(0)))`