If `epsi_(0)` and `mu_(0)` are respectively, the electric permittivity and the magnetic permeability of free space, `epsi` and `mu` the corresponding quantities in a medium, the refractive index of the medium is
A. `(epsilon mu)/(epsilon_(0)mu_(0))`
B. `((epsilon mu)/(epsilo_(0)mu_(0)))^(1//2)`
C. `((epsilon_(0)mu_(0))/(epsilon mu))`
D. `((epsilon_(0)mu_(0))/(epsilon mu))^(1//2)`
