—Did you ask Maria _________?

—Yes. She said she liked it very much. [ ]

A. how did she like the scarf

B. how she liked the scarf

C. what was the scarf like

D. what the scarf was like

如图，一束单色光沿半圆柱形玻璃砖的半径垂直ab面入射，有光线从ab面射出．以O点为圆心，将玻璃砖缓慢转过θ角时，恰好没有光线从ab面射出．光在真空中的速度为c，则（　　）

A．该介质对此单色光的折射率为

B．此单色光在该介质中的传播速度等于c/sinθ

C．此单色光在该介质中的波长是在真空中波长的sinθ倍

D．此单色光在该介质中的频率是在真空中频率的