A converging lens forms a real image `I` on its optic axis. A rectangular galss slab of refractive index `mu` and thickness `t` is introduced between the lens and `I`. `I` will move
A. away from the lens by `t(mu-1)`
B. towards the lens by `t(mu-1)`
C. away from the lens by `t(1-1//mu)`
D. towards the lens by `t(1-1//mu)`