题目

They haven't solved the problem yet ._____she had listened to what he said! A . Only if B . If only C . Even if D . As if 答案：B光的反射定律：光反射时，反射光线、入射光线与法线在同一    内；反射光线和入射光线分别位于法线的    ；反射角    入射角．