题目

完形填空 In our country we think being modest(谦虚的) is a virtue(美德) and being proud is a bad thing. One day, I heard an American boy say to a Chinese student, “you speak very good English.” But the girl answered, “No, no. My English is very poor.” The foreigner was quite 1at the answer. Thinking he had not made himself understood or the girl had not heard him 2 He said, “Yes, indeed, you speak very well.”3 the girl still kept saying. “No.” In the end the American boy could not understand and didn't know 4 to say. What's wrong with the girl's answer? She didn't 5a c正、负电子对撞后湮灭成三个频率相同的光子．已知普朗克恒量为h，电子的质量为m，电荷量为e，电磁波在真空中传播速度为c，则生成的光子射人折射率为的水中，其波长为（ ）A．B．C．D．