题目内容
（请给出正确答案）
A．They use a map and the memory of location.
B．They use the sun and the stars.
C．They use a map and the earth's magnetic field.
D．They have precise sense of time or may use the earth's magnetic field.
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更多“A．They use a map and the memor…”相关的问题
A．They think the screen is a map of the world.
B．They see the screen like a painting.
C．They see the screen like a photograph.
D．They consider what happens on television as a real life.
Science seems to be getting closer to answering a very old mystery (奥秘). Homing pigeons (信鸽) can be taken hundreds of miles from their homes. When they are let to go to fly again, they find their way home. Because of this special ability to find home, pigeons have been used as messengers for hundreds of years.
Today people even breed homing pigeons for racing as a sport. The birds are shipped to some chosen place a few hundred miles away. Then all of them are let to go together. The winner is the bird that gets home first. A good racer can make it home from 500 miles away in a single day.
The mystery of the homing pigeon is how it tells direction and how it finds home.
The first part seems to be pretty well answered, and we know of two ways that pigeons tell directions. First, they use the sun. Experiments show that homing pigeons can tell directions by the sun. What happens when the sky is darkly overcast by clouds and no one can see where the sun is？ Then the pigeons still find their way home.
Naturally, people have wondered whether pigeons might have a built-in compass—something that would tell them about the direction of the earth’s magnetic (磁的) field. Many different kinds of experiments were done. Here’s what the scientists decided after they had made experiments many times. When pigeons can see the sun, they use it as their main means(手段)of direction-finding. When they cannot see the sun, they use some special way to sense direction from the earth’s magnetic field.
But how do pigeons know which direction is toward home？ What do they use that we would call a map？ These are other questions to be answered.
Pigeons have been used as messengers because ______.
A．they have a built-in compass
B．they can cover 500 miles in a single day
C．they have special ability to tell directions
D．they can find their way home
A．They would use it to wash their clothes.
B．They would use it to clean their room.
C．They would carry it home for free.
D．They would use it to avoid mosquitoes.
What do Peter and Linda use their money for？
A．They use their money for food.
B．They use it for their entertainment.
C．They go to the movies and buy records.
A．They don't want to use up all their life savings.
B．They fear they will regret it afterwards.
C．They would like to spend more time with them.
D．They don't want to see their husbands poorly treated.
A．They urge the women to use hormone treatment.
B．The women of high risk should follow the guidelines.
C．They should take some medicine.
D．They urge those women to know their risk of heart attack.
How did people use to respond when their kids got into trouble at school？
A．They'd question the teachers.
B．They'd charge up to the school.
C．They'd tell the kids to calm down.
D．They'd put the blame on their kids.
What is the use of greenhouse gases？
A．They allow energy from the sun to enter but prevent energy from leaving.
B．They allow energy from the sun to leave but prevent energy from entering.
C．They protect the plants.
D．They protect the earth.
听力原文：How is index used to measure the changes in economy？
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A．They use unemployment rates to judge the decline measured by the index.
B．They use the interest rates to confirm the growth of economy.
C．They use percentage to represent the changes weighed by the index.
D．They use stocks as the measurement of development in market.
