题目

某大学数学系共有本科生5000人，其中一、二、三、四年级的人数比为4∶3∶2∶1，要用分层抽样的方法从所有本科生中抽取一个容量为200的样本，则应抽取三年级的学生人数为  （ ）    A．80        B．40    C．60        D．20    答案：思路解析：应抽取三年级的人数为200×=40。    答案：B　　Alexander Bell（亚历山大·贝尔）was an American scientist. He invented the first telephone in 1876. 　　Bell was born in Scotland（苏格兰）. Later he found a job in the United States. He taught the deaf children in a new school. Bell was a very kind man. He liked the deaf children very much. But when he saw the children couldn't hear anything, he felt very sad. He made up his mind to help the children. 　　Bell tried to find a way to send a voice wire（电线）. He thought that spoken words were made up of different vibration（振动）. He thought that if a wire could carry vibrations, it must carry a man's voice. After Bell had the idea, he kept working day after day. He and his assistant worked for about four years. They tried their best to make their wishes come true. 　　One day in 1874, Bell was in one room. But suddenly he heard a sound come from another room. He ran into his assistant's room and shouted. He was very happy because he succeeded at last. Then Bell made his first telephone. But this telephone carried voices only a little way. 　　Later the great Einstein made a better one. Of course, the telephone we use now is much better than Einstein's. (1) Bell was the first man who ________. [　　] A．invented the first telephoneB．taught the deaf children C．worked in AmericaD．had an assistant (2) Bell was born in ________. [　　] A．AmericaB．Australia C．the Great BritainD．Canada (3) Bell ________ so that he could help the deaf children. [　　] A．bought some new toys B．tried his best to make wire carry man's voice C．gave them much money D．lived in America (4) Bell heard the voice that ________. [　　] A．came from his assistant's roomB．made by himself C．came from his friend's roomD．made by a woman (5) The best title of the passage may be ________. [　　] A．A Good TelephoneB．A Kind Man C．Deaf ChildrenD．Bell and the First Telephone