[单选题]
When a light wave enters into a medium of difb* /,, eaf6li3e to tsy yvty/uy,uc5-fer);c8mm cnq2h5axuxl) ent optical density,
A. its speed and frequency change.
B. its speed and wavelength change.
C. its frequency and wavelength change.
D. its speed, frequency, and wavelength change.