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阅读下面短文，从每小题所给的A、B、C、D四个选项中选出最佳选项，并在答题卡上将该项涂黑。
Rats use their tails to help keep body temperature. The rat has specialised blood vessels which control the amount of blood flowing to its tail. Blood flowing into the furless skin of the tail carries heat which is then let out of the body. The rat can direct anywhere between 0.1 and 10 per cent of its cardiac output(心输出量) to the tail. Under ideal conditions, it can get rid of up to 20 per cent of its metabolic(代谢) heat in this way. On the other hand, controlling blood flow to the tail reduces heat loss in cold weather. It is interesting to note that the length of the rat's tail is partly determined by the temperature of the environment in which it is raised.
Observing my three rats suggests that the long tail－usually around the same length as the body－is used for balancing. Although rats cannot grasp objects with their tails, they do seem able to control the muscles along the tail's length with considerable precision(精确). If a rat is running along a narrow surface such as a rope, the tail constantly flicks from side to side to steady them.
When my rats are eating, they rest on the edge of the food bowl, which is about 20 centimetres from the floor of the cage, grasping the bowl with their back paws and eating with their front paws. In doing this their ends stick out quite a long way over the side of the bowl so that it looks as if they should fall off backwards.
As an experiment, I moved the food bowl to about 10 centimetres above the floor of the cage, which is about the length of a rat's tail. Now, instead of curling their tails under the bowl, the rats stretch out their tails and point them straight down so that they touch the floor, supporting their bodies with this “third leg”.
1．A rat's tail is useful in the way ________.
[ ]
A．of controlling the amount of blood flowing
B．to direct its cardiac output
C．of keeping balance and maintaining body temperature
D．to be used as another leg
2．What is true about the rat's tail according to the passage?
[ ]
A．The temperature of where the rat grows determines the length of its tail.
B．The tail is more or less as long as its body.
C．More blood will flow to the tail in cold winter weather to keep it warm.
D．It can get rid of 20% of its metabolic heat under any weather condition.
3．Which of the following has nothing to do with keeping balance?
[ ]
A．The tail flicks from side to side when a rat is running along a rope.
B．The tail sticks out quite a long way curling over the side of the bowl.
C．The tail stretches out straight down to touch the floor like a “third leg”.
D．The tail reduces the body temperature bay letting out heat from it.
4．Which one of the statements below is a wrong description?
[ ]
A．The rat uses fore and hind paws as well as its tail when eating in a bowl.
B．It's better to have the bowl 10 to 20 cm above the cage floor when feeding rats,
C．Rats sometimes uses their tails to grasp things they want.
D．Home-raised rats are more skilled at using their tails.
查看习题详情和答案>>阅读下面短文, 掌握其大意, 然后从1-25各题所给的四个选项中, 选出一 个最佳答案。
A photographer is a person who takes photos as a business or an art. It is often thought that his work is not only full of 1 but is very safe as well, and no one can imagine how 2 his work 3 .
Two photographers were 4 through a thick forest in Alaska, 5 at capturing (capture 抢拍) the wild-life on film. As there was nothing interesting to take pictures of, they were feeling 6 when they 7 sightof a brown bear that had caught a large fish by a quiet brook. The wild beast found them too, and stood on its 8 legs to get 9 sight of the two men. While doing this, the bear made a wonderful pose (n. 姿势) for the two 10 photographers.
Suddenly the bear 11 at them, while the two men kept right on taking photos of the 12 beast. As the beast was 13 very fast towards them, one of the men turned around right away and rushed to a tall tree nearby. He 14 to the top of the tree as quickly as he could. The other man, who could not climb a tree, 15 lay down on the ground, pretending 16. When the bear 17 over him and snuffed (vt.嗅) him all over, the man shut his eyes tightly, 18 his breath and 19 make any movement. While all this was going on, the man in the tree was 20 pictures of the 21 scenes. After a while, the bear went away 22, because bears 23 dead men.
When all was safe, the photographer in the tree came down and said to his friend, "The same story 24 was told in Aesep's Fables (伊索寓言) has just happened to us, and I 25 no chances to take the photos of the wonderful scenes!"
1. A. happiness B. glad C. sadness D. pleasure
[ ]
2. A. interesting B. dangerous C. useful D. important
[ ]
3. A. sometimes is B. always is C. is usually D. usually is
[ ]
4. A. running B. riding C. travelling D. driving
[ ]
5. A. good B. wanting C. planning D. aiming
[ ]
6. A. sorry B. satisfied C. comfortable D. helpless
[ ]
7. A. lost B. caught C. were in D. were out of
[ ]
8. A. fore B. left C. right D. hind
[ ]
9. A. a different B. the same C. a better D. better
[ ]
10. A. mad B. funny C. happy D. excited
[ ]
11. A. stared B. jumped C. shouted D. looked
[ ]
12. A. pleased B. angry C. worried D. funny
[ ]
13. A. rolling on B. jumping up C. drawing on D. running out
[ ]
14. A. climbed B. reached C. jumped D. walked
[ ]
15. A. slowly B. immediately
C. after some delay D. after some time
[ ]
16. A. to be dead B. to die
C. to be dying D. to have died
[ ]
17. A. bent B. sat C. lay D. took
[ ]
18. A. took B. held C. was out of D. taking
[ ]
19. A. daren't B. tried not to
C. not trying to D. not tried to
[ ]
20. A. busy to take B. ready to take
C. busy taking D. worth taking
[ ]
21. A. strange B. beautiful C. famous D. exciting
[ ]
22. A. excitedly B. disappointedly (失望地)
C. gladly D. sadly
[ ]
23. A. never eat B. don't like
C. never touch D. never tend
[ ]
24. A. as B. that C. which D. what
[ ]
25. A. got B. had C. found D. lost
查看习题详情和答案>>B. he relies much on others
C. some people pretend to be kind
D. some people fail to see the kindness in others
B. They waited with patience.
C. They tried their best to help.
D. They put on their flashlights too.
B. accept help from others
C. admit our weakness
D. show our bravery
B. Weakness and Kindness.
C. Weakness and Strength.
D. A Driving Experience.
阅读理解
There is no living creature that does not need sleep or complete rest every day. If you want to know why, just try doing without sleep for a long period of time! You will discover that your mind and body would easily be made angry and find it hard to think clearly or bring your attention on your work. So sleep is quite simply the time when the cells (细胞) of your body recover from the work of the day and build up supplies of energy for the next period of activity.
One of the things we all know about sleep is that we are unconscious (无知觉的) in sleep. We do not know what is going on around us. But that does not mean the body stops all the activities. The necessary organs (器官) continue to work during sleep, but most of the body functions (功能) are slowed down. Your body temperature becomes lower when you are sleeping, which is the reason why people go to sleep under some kind of covers.
And even though you are unconscious, many of your reflexes (反应能力) still work. For example, if someone touches your foot slightly, you will put it away in your sleep, or even brush a fly from your forehead. You do these things without knowing it.
1．If a man did not sleep for a long time, ________ .
[ ]
A．his mind would become tired but his body could work properly
B．it would be hard to make him angry
C．he would not think clearly or bring his attention on his work
D．he would become tired out but could keep on working
2．Sleep can not________.
[ ]
A．make your body recover
B．build up your strength
C．add your cells
D．be helpful to your mind
3．When you are asleep, ________ .
[ ]
A．it is hard for you to know what is going on around
B．you stop all the activities
C．your necessary organs stop working
D．your body functions are all slowed down
4．According to the text, we know that ________ .
[ ]
A when a person is sleeping, his body temperature becomes lower
B．in someone’s sleep, he knows nothing except for his sleeping
C．it’s possible for someone to brush a fly from his fore-head with consciousness in his sleep
D．one can sleep so deeply even that your touching his foot can not cause his reflex
查看习题详情和答案>>
E
As a result of pollution , Lake Erie , on the borders of the USA and Canada, is now without any living things.
Pollution in water is not simply a matter of “poisons” killing large numbers of fish overnight. Very often the effects of pollution are not noticed for many months or years because the first organism(生物体 ) to be affected are either plants or plankton. But these organisms are the food of fish and birds and other creatures. When this food disappears, the fish and birds die too. In this way a whole food chain can be wiped out, and it is not until dead fish and water birds are seen at the river’s edge or on the sea shore that people realize what is happening.
Where do the substances which pollute the water come form? There are two main sources sewage (污水) and industrial waste. As more detergent (洗涤剂 ) is used in the home, so more of it is finally put into our rivers. lakes and seas. Detergents harm water birds dissolving the natural substances which keep their feathers waterproof. Sewage itself, if not properly treated, makes the water dirty and prevents all forms of life in rivers and the sea from receiving the oxygen they need. Industrial waste is even more harmful since there are many highly poisonous things in it, such as copper and lead(铅 ).
So , if we want or stop this pollution , the answer is simple: sewage and industrial waste must be made clean before flowing into the water. It may already be too late to save some rivers and lakes, but others can still be saved if the correct action is taken at once.
72. Pollution in water is noticed _____.
A. when the first organisms are affected B. when a good many fish and birds die
C. when poisonous things are poured into water
D. as soon as the balance of nature is destroyed
73. The living things die because there is no ____ in the lake or river.
A. water B. fish C. poison D. oxygen
74. Which of the following is harmful according to the passage?
A. Organisms B. Plants and plankton in the water
C. Waste water from cleaning D. Industrial waste made clear before flowing into the water
75.The way to stop water pollution is _______.
A. realize the serious situation clearly
B. put oxygen into the river
C. make the waste material harmless before flowing into the water
D. make special room in the sea for our rubbish