题目

I have two _______ and three bottles of _________ here.   A. orange, orange          B. oranges, oranges   C. oranges, orange         D. orange, oranges 答案：C19．如图所示，F、O分别为凸透镜的焦点和光心，请分别画出图中3条入射光线经过凸透镜后的折射光线．