Nuclear power’s danger to health, safety, and even life itself can be summed up in one word: radiation.
Nuclear radiation has a certain mystery about it, partly because it cannot be detected by human senses. It can’t be seen or heard, or touched or tasted, even though it may be all around us. There are other things like that. For example, radio waves are all around us but we can’t detect them, sense them, without a radio receiver. Similarly, we can’t sense radioactivity without a radiation detector. But unlike common radio waves, nuclear radiation is not harmless to human beings and other living things.
At very high levels, radiation can kill an animal or human being immediately by killing masses of cells in vital organs. But even the lowest levels can do serious damage. There is no levels of radiation that is completely safe. If the radiation does not hit anything important, the damage may not be serious. This is the case when only a few cells are hit, and if they are killed immediately, your body will replace the dead cells with healthy ones. But if the few cells are only damaged, and if they reproduce themselves, you may be in trouble. They can grow into cancer. Sometimes this does not show up for many years.
This is another reason for some of the mystery about nuclear radiation. Serious damage can be done without the victim being aware at the time that damage has occurred. A person can be irradiated（辐射）and feel fine, then die for cancer five, ten, or twenty years later as a result. Or a child can be born weak as a result of radiation absorbed by its grandparents.
Radiation can hurt us. We must know the truth.
1.What is the main idea of the passage?
A. How to detect nuclear radiation.
B. How radiation kill a man.
C. The mystery about nuclear radiation.
D. Serious damage caused by nuclear radiation.
2.Which of the following statements is true?
A. Nuclear radiation can cause cancer to human beings.
B. Nuclear radiation can be safe to human beings if its level is low.
C. Nuclear radiation can be detected by human senses.
D. Nuclear radiation is just like common radio waves.
3.What is not the reason why nuclear radiation has a certain mystery?
A. The hurt cells can stay in the body many years and then grow into cancer.
B. It can do harm to a person while the victim isn't aware the damage has occurred.
C. Nuclear radiation can kill a person very easily.
D. Radiation can seldom kill a person immediately.
4.If a human being is hit by nuclear radiation, he may _______.
A. die of cancer after many years B. die immediately
C. have a child who may be born weak D. all of the above
Farmers, especially in developing countries, are often criticized for cutting down forests. But a new study suggests that many farmers recognize the value of keeping trees.
Researchers using satellite images found at least ten percent tree cover on more than one billion hectares of farmland. That is almost half the farmland in the world. Earlier estimates were much lower but incomplete. The authors of the new study say it may still underestimate the true extent worldwide.
The study found the most tree cover in South America. Next comes Africa south of the Sahara, followed by Southeast Asia. North Africa and West Asia have the least.
The study found that climate conditions alone could not explain the amount of tree cover in different areas. Nor could the size of nearby populations, meaning people and trees can live together. There are areas with few trees but also few people, and areas with many trees and many people. The findings suggest that things like land rights, markets or government policies can influence tree planting and protection.
Dennis Garrity, who heads the World Agroforestry Center, says farmers are acting on their own to protect and plant trees. The problem, he says, is that policy makers and planners have been slow to recognize this and to support such efforts.
The satellite images may not show what the farmers are using the trees for, but trees provide nuts, fruit, wood and other products. They also help prevent soil loss and protect water supplies. Even under drought(干旱)conditions, trees can often provide food and a way to earn money until the next growing season.
Some trees act as natural fertilizers. They take nitrogen(氮气)out of the air and put it in the soil. Scientists at the Center say the use of fertilizer trees can re-duce the need for chemical nitrogen by up to three-fourths. Trees also capture carbon dioxide, a gas linked to climate change.
1.Through the study, the researchers found that .
A. there are more trees on farmlands than expected
B. fewer trees are being cut in developing countries
C. most farmers still don’t realize the value of trees
D. trees play a key role in preventing climate change
2.Which of the following has the least tree cover?
A. Southeast Asia B. West Asia.
C. South America. D. Africa south of the Sahara.
3.In Dennis Garrity’s opinion, .
A. most farmers care about nothing but their own interests
B. there are usually few people living in areas with few trees
C. government plays a small role in tree planting and protection
D. government should support farmers in planting and protecting trees
4.The sixth paragraph mainly tells about .
A. how farmers plant trees
B. what products trees can bring
C. the importance of trees to farmers
D. the environmental value of tree cover
Dreams can be familiar and strange, fantastical or boring, but some dreams might be connected to the mental processes that help us learn. In a recent study, scientists found a connection between nap-time dreams and better memory in people who were learning a new skill.
In the study,99 college students between the ages of 18 and 30 each spent an hour on a compute, trying to get through a virtual maze（迷宫）.The maze was different place each time they tired—making it even more difficult. They were also told to find a particular picture of a tree and remember where it was.
For the first 90 minutes of a five-hour break, half of the participants stayed awake and an half were told to take a short nap .Participants who stayed awake were asked to describe their thoughts. Participants who took a nap were asked about their dreams before sleep and after sleep—and they were awakened within a minute of sleep to describe their dreams.
Stickgold, a neuroscientist（神经科学家）,wanted to know what people were dreaming about when their eyes weren＇t moving during sleep.
Four of the 50 people who slept said their dreams were connected to the maze. Some dreamed about the music that had been playing when they were working ; others said they dreamed about seeing people in the maze. When these four people tried the computer maze again, they were able to find the tree faster than before their naps.
Stickgold suggests the dream itself doesn‘t help a person learn—it＇s the other way around.He suspects that the dream was caused by the brain processes associated with learning.
All four of the people who dreamed about the task had done poorly the first time, which makes Stickgold wonder if the dreams show up when a person finds a new task particularly difficult. People who had other dreams, or people who didn＇t take a nap, didn＇t show the same improvement.
1.Before having a short nap, participants of the experiment were asked to .
A. stay in a different place in the maze
B. design a virtual maze which is difficult to get through
C. experience the experiment and try to remember something
D. get through a virtual maze on a computer from the same place
2.What can we learn from the text?
A. Participants who took a nap were required to express their thoughts.
B. Some dreams may encourage people to invent something new.
C. Participants who dreamed about films could finish the task more easily.
D. Participants whose dreams had something to do with the maze could find the tree faster.
3.According to Stickgold, .
A. every person may dream about what they learned
B. people＇s brain processes may still be connected with their learning in their dreams
C. once people＇s eyes stop moving, they are sure to dream about something
D. no matter how fantastical or boring, dreams are connected with people＇s life
4.What is the best title for this text?
A. Dreams Are Strange B. Not All Dreams Are True
C. Dreaming Makes Perfect D. Stickgold, a Dream Expert
Music to My Ears
Robby was 10 for his first piano lesson in my class. Much as he tried, he ____ even the basic rhythm. However, he dutifully reviewed the pieces that I required.
Over the months he tried and tried while I ____ and encouraged him. At the end of each lesson he'd always say, "My mom's going to hear me play some day." ____ it seemed hopeless.
I only knew his mother from a ____as she waited in her aged car to pick him up. Then one day Robby stopped coming. I was secretly ____ that he stopped because of his lack of ability.
Weeks later I informed the students, including Robby, of the coming recital（独奏）. To my ____, Robby asked me if he could be included. I told him he really did not qualify because he had ____ out. He said his mom had been sick and unable to take him to lessons but he was still ____ .
“I've just got to play!" he ____. Something inside me let me allow him to.
Then came the recital night. The gym was ____ with parents. I put Robby up ____, thinking that I could save his poor performance through my “curtain closer（谢幕）.”
The recital went off smoothly. Then Robby came up on stage. His clothes were wrinkled and his hair was ____. "Why didn't his mother at least make him comb his hair for this special night?" I thought.
Robby pulled out the piano bench and began. I was not ____ for what I heard next. His fingers were ____ on the keys. Never had I heard Mozart played so well by people of his age. After he ended, everyone was ____ their feet in wild applause.
In ____ I ran up on stage and put my arms around Robby. "I've never heard you play like that, Robby! How did you ____ it?"
Robby explained, "Well, Miss Hondorf…remember I told you my mom was sick? …____ she had cancer and passed away yesterday. She was born deaf, so tonight she could hear me play in heaven. I wanted to make it special."
There wasn’t a ____ eye in the house. That night I felt he was the teacher and I was the pupil, for it was he who taught me the meaning of perseverance and ____.
1.A. had B. lacked C. showedD. got
2.A. learned B. checkedC. listened D. played
3.A. And B. ButC. SoD. Or
4.A. conversation B. performanceC. distanceD. picture
5.A. guiltyB. anxiousC. glad D. sad
6.A.surprise B. reliefC. pleasureD. satisfaction
7.A. steppedB. wornC. runD. dropped
8.A. actingB. practicingC. performingD. recording
9.A. insistedB. suggestedC. complainedD. threatened
10.A. packedB. linedC. piledD. covered
11.A. least B. mostC. firstD. last
12.A.cool B. messy C. neat D. dull
13.A. eager B. concernedC. preparedD. grateful
14.A. hesitating B. crawling C. touchingD. dancing
15.A. over B. underC. inD. on
16.A. chaos B. return C. silenceD. tears
17.A. find B. feelC. makeD. like
18.A. Gradually B. SuddenlyC. FrequentlyD. Actually
19.A. bright B. curiousC. dryD. wet
20.A. love B. talent C. regretD. courage
“I hope the dialogue,” said the spokesman, “______ between the two presidents next week will give us some active signals.
A. making B. to make C. to be made D. made
This restaurant has an inviting, homelike atmosphere ___ many others are short of.
A. whereB. when C. that D. what
