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问题 问答题

某同学做“研究凸透镜成像规律”的实验，当他将蜡烛、透镜、光屏的位置调节到屏上出现一个清晰的像时，发现光屏上的像比较小，为了获得较大的像，在不改变透镜位置的情况下，他应进行的操作是：

①______；

②______，直至光屏上出现清晰的像为止．

答案

要想使物体通过凸透镜成的实像变大，就要使物体靠近凸透镜，减小物距；由于物距的减小，导致了像距的变大，所以要同时使光屏远离凸透镜．

①将蜡烛向透镜方向移动； ②将光屏向远离透镜的方向移动；故答案为：

故答案为：①将蜡烛向透镜方向移动； ②将光屏向远离透镜的方向移动．

改错题

修改病句。

（1）“神舟”七号的成功发射让世界对中国另眼再看。

___________________________________________________________

（2）远处，几座小山在云雾中若隐若现看不清楚。

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单项选择题

Government officials reported three new cases of mad cow, bringing the total so far this year to 99. Last year, France recorded just 31 cases of the mad cow disease. The rising numbers are in part (1) a new testing program that focuses on cows that are most (2) . That program has (3) 39 cases. But still 60 new cases were identified in the usual way, (4) were found in 1999. Many scientists (5) that this year, five years after safety precautions were (6) , the number of cases would be (7) .

The rise in cases has (8) some scientists to question whether the disease can be transmitted in ways not yet understood. Scientists are still (9) the disease, first recognized in cows in 1986.

It appears that it is not caused by a bacteria, virus or fungus, but (10) infectious particles called prion, perhaps (11) a virus or other agent. The disease kills cells in the brain, (12) it spongy and full of holes.

France has taken more steps to (13) safety than most European countries, (14) refusing to take English beef (15) the European Union. But some scientists believe that France has not been (16) in imposing the ban on feed that (17) animal pans.

Some French officials hope that the sudden interest in mad cow disease will mean that French consumers will become educated about it, thereby recognizing that French beef is actually (18) controlled. Every cow is given a passport at birth, and extensive information about its parentage and (19) it was raised must be (20) to any slaughterhouse. When a diseased animal is found, the entire herd is destroyed.

17（）

A. contains

B. consists of

C. is made from

D. is made up of
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