The correct answer is: C. wavelength and speed.
When light passes from air into glass, it slows down and its wavelength changes. The frequency of light does not change, because frequency is related to the energy of the light, and the energy of light does not change when it passes from one medium to another.
The speed of light in a medium is given by the equation $v = \frac{c}{\mu}$, where $c$ is the speed of light in a vacuum and $\mu$ is the refractive index of the medium. The refractive index of glass is about 1.5, which means that light travels 1.5 times slower in glass than it does in a vacuum.
The wavelength of light is given by the equation $\lambda = \frac{v}{f}$, where $v$ is the speed of light and $f$ is the frequency of light. Substituting the equation for $v$ into this equation, we get $\lambda = \frac{c}{\mu f}$. This shows that the wavelength of light is inversely proportional to the refractive index of the medium. Therefore, when light passes from air into glass, where the refractive index is greater, the wavelength of light decreases.