―Could I use your computer for a few moments, please?  

― _____. I’m not using it myself.

A．Come on

B．Go ahead

C．It depends

D．That’s great

折光率是

A．折射角的角度

B．入折射角与折射角角度的比值

C．折射角与入射角角度的比值

D．入射角正弦与折射角正弦的比值

E．入射角余弦与折射角余弦的比值