[单选题]
When a light wave enters into 5mnagjoz ;qbo: 2qzmohb ,js (-gbg99q3j*g , a medium of different3ra7 bpf, qd0n.42sozv.jioth; 9 ejz 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.