-- Could you tell me __________ yesterday?
-- Because my bike was broken on my way here.
A:why you came late
B:why do you come late
C:why you come late
D:why did you come late
多音字注音并组词
盛:____ ( ____)
____ ( ____)
如图所示,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.则该玻璃砖的折射率为( )