Answer:
A. The two materials have matching indices of refraction.
Step-by-step explanation:
We know that when light moves from one medium to another, usually, it undergoes a process of bending, called Refraction.
This is due to the fact that the two media have different indices of refraction. This means that when the light wave enters the second medium from the first, its speed changes (and ultimately, its wavelength also changes).
So, if light passes through an interface between two media and the direction of the propagation of light does not change, then, it would mean that both media have the same refractive index.