多项选择题

关于国家政治地理特征的论述，正确的有：（）。

A．领土是国家最基本的政治地理结构
B．领土形状对一国没有政治地理意义
C．一国不一定只有一个首都
D．河流划分国界原则是：采用河流主流线作为界线

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听力原文： W: Well, Mr. Steve, we have had an interesting discussion about your work. Now, tell us something about you after work activities.M: I guess not much different from everyone elsE.I'm fond of sport, and I run about 3 miles every day. I particularly enjoy cross-country running, where you have to run across fields, jump over streams and so on. While I'm running I think about all kinds of things, and at the end of a run I'm sometimes surprised to find that I've managed to solve a problem that was on my minD.Next year I'm going to try the London Marathon. It's a long, hard race--26 miles, or 42 kilometres and you have to be tough to finish, but I very much want to do it. I worry a hit about getting old, and I'd like to prove to myself that I'm still almost as well as I was twenty years ago.I'm interested in climbing as well as running. I'll never become an expert climber, but I know what I'm doing in the mountains. I successfully completed a course in snow and ice climbing when I was younger, and I've done a lot of easy climbs in the Alps during the last few years. My wife doesn't share my interest in mountains. She agreed to go climbing with me once, but she found that she felt sick as soon as she reached above 1, 000 metres, so we decide to follow different hobbies.W: You certainly seem to enjoy various types of recreation. All right, My Smith. Thanks for your interesting talk.What are the man's hobbies?A.Running and thinking.B.Running and jumping.C.Running and climbing.D.Running and skiing.

A.What
B.Running
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B.Running
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C.Running
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D.Running
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Birds that are literally half-asleep---with one brain hemisphere alert and the other sleeping- control which side of the brain remains awake, according to a new study of sleeping ducks.Earlier studies have documented half-brain sleep in a wide range of birds. The brain hemi- spheres take turns sinking into the sleep stage characterized by slow brain waves. The eye con- trolled by the sleeping hemisphere keeps shut, while the wakeful hemisphere' s eye stays open and alert. Birds also can sleep with both hemispheres resting at oncE.Decades of studies of bird flocks led researchers to predict extra alertness in the more vulnerable, end-or-the-row sleepers. Sure enough, the end birds tended to watch carefully on the side away from their companions. Ducks in the inner spots showed no preference for gaze direction.Also, birds dozing(打盹) at the end of the line resorted to single-hemisphere sleep, rather than total relaxation, more often than inner ducks diD.Rotating 16 birds through the positions in a four-duck row, the researchers found outer birds half-asleep during some 32 percent of dozing time versus about 12 percent for birds in internal spots.'We believe this is the first evidence for an animal behaviorally controlling sleep and wakefulness simultaneously in different regions of the brain, 'the researchers say.The results provide the best evidence for a long-standing supposition that single-hemisphere sleep evolved as creatures scanned for enemies. The preference for opening an eye on the lookout side could be widespread, he predicts. He's seen it in a pair of birds dozing side-by-side in the zoo and in a single pet bird sleeping by a mirror. The mirror-side eye closed as if the reflection were a companion and the other eye stayed open.Useful as half-sleeping might be, it's only been found in birds and such water mammals(哺乳动物) as dolphins, whales, and seals. Perhaps keeping one side of the brain awake allows a sleeping animal to surface occasionally to avoid drowning.Studies of birds may offer unique insights into sleep. Jerome M. Siegel of the UCLA says he wonders if birds' half-brain sleep “is just the tip of the iceberg (冰山)”. He speculates that more examples may turn up when we take a closer look at other species.A new study on birds' sleep has revealed that _________.A.half-brain sleep is found in a wide variety of birdsB.half-brain sleep is characterized by slow brain wavesC.birds can control their half-brain sleep consciouslyD.birds seldom sleep with the whole of their brain at rest

A.B.
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A.half-brain
J.half-brain
K.birds
L.birds