A．DSB．CSC．SSD．CS和SS

No more than twenty years passed () laser was first invented.

A、after

B、since

C、before

D、when

The boy passed the finial exams. But if he had spent more time on them, the results (be) ______much better.

t school.

A.the most happiest time

B.a more happier time

C.much happy time

D.a much happier time

The boy passed the finial exams. But if he had spent more time on them, the results (be) ________ much better.

】______ , scientists discovered how to split atoms decades【C3】______ the invention of the atomic bomb and the use of【C4】______ power to produce electricity. But sometimes discovery and【C5】______ happen at the same time, as occurred more than thirty years ago【C6】______ the discovery of coherent light and the invention of the laser.

The word laser【C7】______ "light amplification by stimulated emission of radiation. To many people, lasers are very mysterious, but a laser is simply a【C8】______ that produces a strong light. The light from the laser is called【C9】______ light because it is light that only moves in one direction.【C10】______ , incoherent light, like the light from the sun or light from a bulb, moves away from its source【C11】______ all directions, so its strength is very spread out. The light from a laser, moving in only one direction and【C12】______ in a narrow beam, is much stronger. Laser light is created by a【C13】______ called stimulated emission. In this process, the atoms of a certain substance, such as a crystal or a gas, are excited 【C14】______ that they produce coherent light. A person working with a laser can aim this coherent light,【C15】______ a laser beam, in any direction.

As soon as the laser was developed, scientists began thinking of practical applications【C16】______ it. One of the earliest uses was to make extremely precise measurements of distance and speed.【C17】______ , the distance to the moon was measured to within a foot, and the speed of light was measured to 【C18】______ a thousandth of a mile per second. As time【C19】______ , many more applications for the laser were【C20】______ .

【C1】

A．long

B．early

C．very

D．earlier

C2】______ , scientists discovered how to split atoms decades 【C3】______ the invention of the atomic bomb and the use of 【C4】______ power to produce electricity. But sometimes discovery and 【C5】______ happen at the same time, as occurred more than thirty years ago 【C6】______ the discovery of coherent light and the invention of the laser.

The word laser 【C7】______ "light amplification by stimulated emission of radiation." To many people, lasers are very mysterious, but a laser is simply a 【C8】______ that produces a strong light. The light from the laser is called 【C9】______ light because it is light that only moves in one direction. 【C10】______ , incoherent light, like the light from the sun or light from a bulb, moves away from its source 【C11】______ all directions, so its strength is very spread out. The light from a laser, moving in only one direction and 【C12】______ in a narrow beam, is much stronger. Laser light is created by a 【C13】______ called stimulated emission. In this process, the atoms of a certain substance, such as a crystal or a gas, are excited 【C14】______ that they produce coherent light. A person working with a laser can aim this coherent light, 【C15】______ a laser beam, in any direction.

As soon as the laser was developed, scientists began thinking of practical applications 【C16】______ it. One of the earliest uses was to make extremely precise measurements of distance and speed. 【C17】______ , the distance to the moon was measured to within a foot, and the speed of light was measured to 【C18】______ a thousandth of a mile per second. As time 【C19】______ , many more applications for the laser were 【C20】______ .

【C1】

A．long

B．early

C．very

D．earlier

______in doing an examination, the time passed by quickly.

A．Being absorbed

B．Having been absorbed

C．When they were absorbed

D．Be absorbed

If there were no examinations, we should have ______ at school.

A．the happiest time

B．a more happier time

C．much happiest time

D．a much happier time

rovement for Chinese's living conditions？

F: Oh, no. This time the men were imported as work crews to construct the first transcontinental railroad. They were sorely needed because the work was so strenuous and dangerous, and it was carried on in such a remote part of the country that the railroad company could not find other laborers for the job. As their predecessors, these Chinese were almost all males.

M: And I guess they, too, encountered a great deal of prejudice？

F: Exactly. The hostility grew especially strong after the railroad project was completed, and the imported laborers returned to California--thousands of them, all out of work.

M: And their days were even harder？

F: Yes. Because there were so many more of them this time, these Chinese drew even more attention than the earlier group did. They were so very different in every respect.

M: I think so. Like their physical appearance, the long pigtail at the back of their otherwise shaved heads; the strange, non- Western clothes, the speech, and their religion.

F: What's more, when times were hard, they were blamed for working for lower wages and taking jobs away from white men. Anti-Chinese riots broke out in several cities. Chinese were barred from using the courts and also from becoming American citizens. Finally, in 1882, the Congress passed the Chinese Exclusion Act, which stopped the immigration. Many Chinese returned to their homeland, and their numbers declined sharply in the early part of this century.

When did many more Chinese arrive in California？

A．in the early 1850' s.

B．in the late 1850' s

C．in the early1860' s.

D．in the late 1860' s.

rovement for Chinese's living conditions？

F: Oh, no. This time the men were imported as work crews to construct the first transcontinental railroad. They were sorely needed because the work was so strenuous and dangerous, and it was carried on in such a remote part of the country that the railroad company could not find other laborers for the job. As their predecessors, these Chinese were almost all males.

M: And I guess they, too, encountered a great deal of prejudice？

F: Exactly. The hostility grew especially strong after the railroad project was completed, and the imported laborers returned to California--thousands of them, all out of work.

M: And their days were even harder？

F: Yes. Because there were so many more of them this time, these Chinese drew even more attention than the earlier group did. They were so very different in every respect.

M: I think so. Like their physical appearance, the long pigtail at the back of their otherwise shaved heads; the strange, non- Western clothes, the speech, and their religion.

F: What's more, when times were hard, they were blamed for working for lower wages and taking jobs away from white men. Anti-Chinese riots broke out in several cities. Chinese were barred from using the courts and also from becoming American citizens. Finally, in 1882, the Congress passed the Chinese Exclusion Act, which stopped the immigration. Many Chinese returned to their homeland, and their numbers declined sharply in the early part of this century.

When did many more Chinese arrive in California？

A．in the early 1850's.

B．in the late 1850's

C．in the early1860's.

D．in the late 1860's.