Light travels in a straight line (rectilinear propagation of light). This statement does hold if the medium of travel for light is A. Of variable refractive index B. Made up of slabs of different refractive indices C. Homogeneous and transparent D. Inhomogeneous and transparent

The correct answer is C. Homogeneous and transparent.

Light travels in a straight line (rectilinear propagation of light) only if the medium of travel for light is homogeneous and transparent. This means that the medium must have the same refractive index throughout and must not absorb or scatter light.

If the medium is inhomogeneous, meaning that the refractive index is not the same throughout, then light will bend as it travels through the medium. This is called refraction.

If the medium is opaque, meaning that it absorbs or scatters light, then light will not travel in a straight line. This is because the light will be absorbed or scattered by the medium before it can reach

Therefore, the only option that satisfies both of these conditions is C. Homogeneous and transparent.