题目

Last summer I took a course on        poisonous gases.   A. how to deal with                                      B. what to deal with     C. how to be dealt with                                   D. what to be dealt with 答案：A一束光线射向平面镜，请根据图中给出的入射光线AO画出对应的反射光线OB，法线NO，由图可知，光路被改变了______度．