什么是反射定律？
参考答案：
反射线位于入射面和界面法线组成的法平面内，反射角等于入射角。
计算：（﹣a）2÷a=( )。
He seemed to be looking for the words ____ he could express his idea.
A．for which
B．with which
C．in whom
D．in that
