In the case of refraction of light :
a) Frequency changes
b) Speed changes
c) Wavelength changes

In the process of refraction, speed of light and wavelength of light changes. 

In a medium, speed of light is given by $v=\frac{c}{\mu }$  where $\mu$ is refractive index of the medium. Hence, for medium with different refractive index , speed of light is different. 

Frequency will not change because at the boundary/interface of the medium, the number of waves you send is the number of waves you receive at the other side, almost instantly. 

Since, for a travelling wave we have a relation $\nu =\frac{v}{\lambda }$. 

Hence wavelength also changes in the process of refraction.

So, option B is correct.