Consider the following statements A and B and identify the correct answer
A) The refractive index of the extraordinary ray depends on the angle of incidence in double refraction
B) The vibrations of light waves acquire one sidedness for both ordinary and extraordinary rays in double refraction

In double - refraction the refractive index of the extra - ordinary ray varies according to the direction taken because it has components that  are both parallel and perpendicular to the crystal's optic axis. Thus (A) is correct.
The ordinary ray and the extraordinary ray are polarized in planes vibrating at right angles to each other. Thus (B) is correct.