If `mu_(1)` and `mu_(2)` are the refractive indices of the materials of core and cladding of an optical fibre, then the loss of light due to its leakage can be minimized by having
A. `mu_(1) gt mu_(2)`
B. `mu_(1) lt mu_(2)`
C. `mu_(1) le mu_(2)`
D. `mu_(1) = mu_(2)`