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问题 不定项选择

如图所示，在水平地面上方有正交的匀强电场和匀强磁场，匀强电场方向竖直向下，匀强磁场方向水平向里。现将一个带正电的金属小球从M点以初速度v0水平抛出，小球着地时的速度为v1，在空中的飞行时间为t1。若将磁场撤除，其它条件均不变，那么小球着地时的速度为v2，在空中飞行的时间为t2。小球所受空气阻力可忽略不计，则关于v1和v2、t1和t2的大小比较，以下判断正确的是

[ ]

A.v1＞v2，t1＞t2

B.v1＜v2，t1＜t2

C.v1=v2，t1＜t2

D.v1=v2，t1＞t2

答案

D

单项选择题

In the United States and in many other countries around the world, there are four main ways for people to be (91) about developments in the news: newspapers, magazines, and radio or television news broadcasts. A person may use one, or all, of these (92) for information. Each source is useful in its (93) way. Newspapers and magazines can give much information about a particular event. They may (94) some history of the event, some of its (95) , some of its effects, or perhaps give an (96) or point of view on a particular development. Radio and television can help a person to be well informed about what is happening each day. It is also (97) to listen to radio or watch TV (98) do something else at the same time. Many people can listen to the news on their car radio while driving (99) . For the student of English as a foreign language, an English language newspaper may be the most helpful news source that will also (100) you practice in reading English.
Most daily English language newspapers are not very hard to find. They are interesting and helpful in many (101) . In some of them, you may be able to find news about your (102) country. You will find news and information about important national and international political (103) . (104) what you are interested in, you can probably find something in the newspaper about it. A(n) (105) in the newspaper may help you solve a problem. Other stories may be about good movies, concerts, or TV shows.
Usually, an English language newspaper has several (106) or parts. Each part of the newspaper (107) stories about different kinds of news. Some sections have a lot of advertisements which may be helpful if you want to save money. By reading the advertisements, you may find something you want (108) sale. Or you may find that two stories are advertising the (109) thing, but at one store the price is lower. Other sections may have (110) advertisements or have only a specific type of advertisement to interest the people.

A．but

B．or

C．and

D．still
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单项选择题

下列何灯照明方位不可调节（）

A.PSU上阅读灯

B.固定着陆灯

C.可收放着陆灯

D.标志灯
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