Twothirds of the world"s major rivers have now been disrupted with more than 50
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Twothirds of the world"s major rivers have now been disrupted with more than 50,000 dams in an attempt to store water and provide power.In the US，there are more than 85,000 dams，disrupting large and small rivers，and in most cases transforming natural flow.The most famous of these，the Hoover Dam，constructed in the 1930s，is mainly responsible for the fact that the Colorado River no longer reaches the ocean.
Dams，besides all their attractive benefits，also have negative impacts.Creating a reservoir means a large area must be flooded.Communities may lose their land，houses and culturally important sites.
Environmentally，the new reservoir can be a paradise for wildlife，especially birds；however，it can cause greenhouse gas emissions and poison the water.Also，the dramatic rise and fall of water levels during dam releases is too extreme for plants and animals to cope with，resulting in dead zones around the shores of reservoirs.Fish that lay their eggs in the shallows，for example，may find a few hours later that those sites are high and dry.
Downstream(在下游方向)of a dam，the flow may be reduced so that farmers cannot irrigate their fields.Many rivers run through national borders，which may cause conflict over precious water.Disputes have been continuing between India and Pakistan，and Turkey，Syria and Iraq，for example.
Dams don"t just block the flow of water.They also prevent fish migrations，and dams are a barrier to sediment(沉淀物)flows.Instead of rushing downriver，sediments get backed up against the dam wall，which causes the reservoir level to increase over time.However，sediments which are rich in nutrients have become a problem.The fertility of the entire system can be influenced，with soils lost during seasonal rains not being replaced.
Perhaps the biggest problem can be seen in deltas，which are sinking into the oceans.Groundwater is being extracted to feed the city，causing the city to sink，and sediments washed away by the ocean are no longer being replaced.The result is that sea level rises in cities from Shanghai to Alexandria.
小题1:The Hoover Dam is mentioned in the passage in order to show________.| A．dams play an important role in our life | | B．dams have impacted the flow of the rivers | | C．dams make people lose their land and houses | | D．dams have many benefits as well as side effects |
小题2:What effects does creating a reservoir have on people"s life?
a．People will see fewer birds on the sides of the rivers.
b．Farmers will have less water to irrigate their fields.
c．Visitors can"t visit some cultural relics any more.
d．More conflicts and wars over water will break out.
e．More kinds of fish will become extinct in future.小题3:With many dams built across the rivers，fish ________.| A．will find more places to lay their eggs | | B．will face a dangerous habitat | | C．will be fed on more sediments rich in nutrients | | D．will find it easier to deal with the rise of water |
小题4:How can dams influence large cities like Shanghai?| A．Their entire system will be influenced. | | B．The rainy season will last longer. | | C．They will lie below sea level in future. | | D．Rich soils will be washed away. |
小题5:What does the passage mainly talk about?| A．Environmental loss of dams. | | B．Cultural loss of dams. | | C．Economic gain of dams. | | D．Environmental benefits of dams. |
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答案
小题1:B
小题2:D
小题3:B
小题4:C
小题5:A |
解析
本文主要讲的是人类在世界各地修建的大坝对环境造成的影响。
小题1:解析 细节理解题。根据第一段中的“and in most cases transforming natural flow...no longer reaches the ocean”可知，文章中提到胡佛大坝是为了说明大坝可以影响河的流向，故选B。
答案 B
小题2: 解析 细节理解题。根据第二段末句和第四段首句可知，随着大坝的修建，蓄水淹没了一些文化遗迹，并且导致下游的农民无法灌溉农作物，故选D。
答案 D
小题3:解析 细节理解题。根据第三段中的“it can cause greenhouse gas emissions and poison the water”可知，随着大坝的修建，蓄水会释放出温室气体，使水有毒，所以鱼的生活环境会变得危险，故选B。
答案 B
小题4:解析 细节理解题。根据最后一段中的“which are sinking into the oceans”可知，未来有一天，上海将会被海水淹没，故选C。
答案 C
小题5:解析 主旨大意题。通读全文可知，本文主要讲的是修建大坝对环境造成的影响，故选A。
答案 A |
举一反三
Eyesight problems are common among all ages and if they are left untreated, they can cause serious headaches or other problems. The good news is that most eyesight problems can easily be sorted out by wearing glasses.
Regular eye tests are important for everyone. Children and teenagers, under the age of 16 and up to the age of 19 for those full-time education, have the right to have eye tests for free in Britain. As the eye test is free, there’s no excuse for not having a regular eye test. Doctors suggest that it’s better to have an eye test about once a year.
Wearing glasses isn’t always regarded as all that cool and teens who suddenly need to wear glasses may find it difficult to accept. If they’ve grown up wearing glasses, then they may be more used to it. However, if your eyes are in poor health, not wearing glasses can put even more pressure on your eyes and could make them even worse.
Thankfully, the days of little choice of glasses frames (框架) for teenagers are gone and there’s now a wide selection of frames. If a teen does need to wear glasses, then it’s good to let him or her choose the type, as he or she will be able to choose something he or she feels comfortable. Don’t forget to be guided by the experts on glasses too.
小题1: According to the text, teens in the UK ______.| A．have few eyesight problems | | B．can design their own glasses | | C．change their glasses very often | | D．can check their eyes without paying |
小题2:How often do doctors suggest teens to have an eye test?| A．Once a month. | B．Once every six months. | | C．Once a year. | D．Twice a year. |
小题3:It can be learned from the text that teens ______.| A．find it difficult to buy comfortable glasses | | B．prefer to wear cool glasses at an early age | | C．are advised to wear glasses if their eyesight is poor | | D．think they are much cooler when wearing glasses |
小题4:In the past, teens who wanted to buy glasses ______.| A．were unable to find the right glasses | | B．only had a few styles to choose from | | C．could not find an expert to ask for advice | | D．were worried about the quality of glasses |
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Bad teeth may be painful and it’s getting worse without treatment. They can even ruin your life. Illness of the teeth can find its way into the blood system. This can increase the chances of a heart disease or other illnesses.
Experts say good care for teeth should start at birth. Mothers’ milk is the best food for the healthy development of teeth.
But dentists say a baby’s mouth and early teeth should be cleaned after each feeding. Use a cloth with a little warm water. Do the same if a baby is fed with a bottle. Experts say if you decide to put your baby to sleep with a bottle, give him only water.
When baby’s teeth begin to appear, you can clean them with a wet toothbrush. Dentists say it is important to find soft toothbrushes made especially for babies and to use them very gently. Young children often eat toothpaste (牙膏) when they brush, so they should be carefully watched when they brush their teeth.
Parents often ask what effect thumb sucking (咬手指) might have on their baby’s teeth. Experts generally agree that this is fine early in life. Most children stop sucking their thumbs by the age of four. If it continues, parents should talk to their children’s dentist or doctor.
Dentists say children should have their first dental visit by the time they are one year old. They say babies should be examined when their first teeth appear usually at around six months.
小题1:Why should people pay attention to teeth problems?| A．They can cause other illnesses. | | B．They will bring bad luck. | | C．They will bring the family much trouble. | | D．They usually last a long time. |
小题2: According to the writer, baby’s teeth should be protected from the day ______.| A．he begins to speak | B．he has his first tooth | | C．he was born | D．he is fed with bottle milk |
小题3:The underlined word “it” in Paragraph 5 refers to “_____”.| A．toothache | B．parents’ trouble | C．thumb sucking | D．experts’ advice |
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The weather predictions for Asia in 2050 read like a story from a doomsday movie.
Many experts and green groups fear they will come true unless there is a united global effort to hold back greenhouse gas outpouring. In the decades to come, Asia---home to more than half the world’s 63 billion people-will change from one climate extreme to another, with tired farmers battling droughts, floods, disease, food shortages and rising sea levels.
“It’s not a pretty picture,” said Steve Sawyer, climate policy adviser with Greenpeace in Amsterdam. Global warming and changes of weather patterns are already occurring and there is more than enough carbon dioxide and other greenhouse gases in the atmosphere to drive climate change for decades to come.
Already, changes are being felt in Asia but worse is likely to come, Sawyer and top climate bodies say, and could lead to mass migration and widespread human disasters. According to predictions, icebergs will melt faster, some Pacific and Indian Ocean islands will have to evacuate(疏散) or build sea defenses, storms will become more intense and insect and water-borne diseases will move into new areas as the world warms.
All this comes with rising populations and demand for food, water and other resources. Experts say environmental worsening such as deforestation and pollution will probably enlarge the results of climate change.
In what could be a sign of the future, Japan was hit by a record of 10 typhoons and tropical storms this year, while two-thirds of Bangladesh, parts of Nepal and large areas of northeastern India were flooded, affecting 50 million people, destroying livelihoods and making tens of thousands ill.
The year before, a winter cold struck and a summer heat wave killed more than 2,000 people in India.
小题1:This passage is mainly about .| A．what kind of weather we like best | | B．the weather predictions for Asia in the future and the reasons | | C．how to improve our environment | | D．that the world will not be suitable for us to live in |
小题2:In the future the Asian farmers will have to face the following except .| A．food shortages | B．droughts | C．wars | D．floods |
小题3:The underlined word “doomsday” may give us the feeling of .| A．happiness | B．sadness | C．peace | D．excitement |
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Chinese scientists have found a new way to use cells found in human urine （尿液）that could aid in the treatment of a range of nerve disorders.That is a new technique for reprogramming cells in human urine into nerve progenitor cells that can grow into multi-functional nerve and brain cells.
The technique is expected to be used in the study and treatment of nerve disorders such as Parkinson"s disease, Alzheimer"s disease and other nerve disorders.
Pei Duanqing, a professor at Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, said his research team has combined an episomal system to deliver reprogramming factors with a chemically defined culture medium to reprogram kidney epithelial(肾表皮) cells in urine into NPCs.
These NPCs, normally only found in the human brain, were later proven to be transgene-free and self-renewing, he said.
"These nerve and brain cells can survive for up to one month when transplanted into the brain of a newborn rat," said Pei. "My team is working hard to understand why our experimental condition allowed the urine cells to become NPCs, because we want to improve the technique and make it more efficient".
Scientists have long searched to treat and study neural disorders by obtaining and transplanting neural stem cells. However, the previous method of getting and using cells from either fetal (胎儿)or adult human tissue remains challenging due to ethical concerns and immune system rejections, he said.
Pei hopes the discovery will be used to generate NPCs from patients with nerve disorders such as Parkinson"s disease. "These NPCs from patients may help us discover new drugs for these diseases."
"It is a remarkable advance in the stem cell field. The results and methods obtained from this study will be of great value and significance to the field, " said Fred Gage,a professor with the Salk Institute for Biological Studies.
小题1:What is the passage mainly about?| A．NPCs are beneficial in treating human diseases. | | B．Chinese scientists succeeded in making NPCs from human urine. | | C．Chinese scientists have found cures for all diseases. | | D．A new technique was used to study the use of human urine |
小题2:Pei and his tean try their best to work hard in order to .| A．make more contributions to medical study | | B．discover another new technique | | C．make the technique more perfect | | D．treat more patients suffering from bad diseases |
小题3:What is the challenge of making NPCs in the previous method?| A．The ethical comcerns and immune system refusal | | B．The difificulties in getting cells from human. | | C．The under-developed techniques in medical science. | | D．The lack of financial support from the government. |
小题4:From the last paragraph we can infer .| A．the new technique will be developed in science | | B．the results and methods will be applied to treating cancers | | C．the study will give a major push to the stem cell field | | D．the mew technique will bring great profis |
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Popeye the Sailor first became a popular cartoon in the 1930s. the sailor in that cartoon ate lots of spinach to make him strong. People watched him, and they began to buy and eat a lot more spinach. Popeye helped sell 33 percent more spinach than before! Spinach became a necessary part of many people’s diets. Even some children who hated the taste began to eat the vegetable.
Many people thought that the iron in spinach made Popeye strong, but this is not true. Spinach does not have any more iron than any other green vegetable.
People only thought spinach had a lot of iron because the people who studied the food made a mistake. In the 1890s, a group of people studied what was inside vegetables. This group said that spinach had ten times more iron than it did. The group wrote the number wrong, and everyone accepted it.
Today, we know that the little iron in spinach cannot make a difference in how strong a person is. However, spinach does have something else which the body needs—folic acid.
It is interesting to point out that folic acid can help make a person strong. Maybe it was really the folic acid that made Popeye strong all along.
小题1:A good title for this reading passage is______.| A．Popeye the Sailor | | B．The Truth About Spinach | | C．A Mistake with Numbers | | D．Folic Acid Makes You Strong |
小题2:Why did many people eat spinach after they saw Popeye the Sailor?| A．People liked folic acid. | | B．They thought Popeye was funny. | | C．Spinach had a lot of iron. | | D．They thought spinach made them strong. |
小题3:A research group told people that spinach______.| A．made Popeye strong | | B．was a green vegetable | | C．had less iron than other green vegetables | | D．had more iron than other green vegetables |
小题4:The reading passage says that perhaps Popeye got his strength from______.| A．iron | B．spinach | C．folic acid | D．exercise |
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