题目

一个焦距为30cm的凸透镜，在它的主光轴上离焦点20cm，放置一个物体，则该物体经过凸透镜所成的像一定是的像． 答案：【1】放大 －I'm sorry I ________ my English book at home, Mr．Wang． －Don't forget________ it to school tomorrow, please． [　　] A．forgot; to take B．left; to bring C．forgot; to bring D．left; to take