题干
Mr. Black is always patient _____ us students and guides us ______ a lot better in math.
A：in, to do
B：at, doing
C：with, to do
D：to, doing
答案(点此获取答案解析）
C
Mr. Black is always patient _____ us students and guides us ______ a lot better in math.
A：in, to do
B：at, doing
C：with, to do
D：to, doing
和
都是已知的，紧贴直角边AC的是一块平面镜，将一束光线SO入射到棱镜的AB面上，适当调整SO的入射方向，使从AB面出射的光线与入射光线SO恰好重合，在这种情况下，仅需要测出一个物理量
就可以算出该棱镜的折射率，则计算折射率的表达式为( )
