6、The pollution of groundwater by nitrates(硝酸盐)is of concern to public health authorities and environmental organizations because high nitrate concentration(高硝酸含量)s in drinking water can cause methaemoglobinaemia(高铁血红蛋白血)in infants.Another environmental problem associated with high nitrate concentration in groundwater is eutrophication(富营养化)of receiving waters(供水).Virtually all decisions about the control of nitrate pollution of ground water are made in the face of uncertainties that frustrate(阻止，挫败)efforts to guarantee the desired results.The decisions also have to be made in an adversarial(意见相左，敌对不可调和的)environment in which the goals of society and those of the agricultural sector(农业部门)are often different.

3. Passage Twenty-FiveOnline dating has just been revealed to be one of the most common ways to start a relationship.But new research reveals that the concept is still highly flawed (有缺陷的).An analysis of 400 studies into online dating shows that while it offers access to plenty of other singles， users can be overwhelmed and put off by the volume of choice， defeating the purpose.The research， by Northwestern University and published in the journal Psychological Science in the public interest， found that the processes involved don’t lend themselves to forming strong relationships.The findings also indicated that the concept of an online profile (介绍)is not entirely useful and “can result in treating potential partners as mere objects”.Lead author Eli.J.Finkel explained， “Online dating is a terrific addition for singles to meet.However， there are two problems.” First， studying over seemingly endless lists of profiles of people one does not know， as on Match.com， does not reveal much about them.Second， it “overloads people and they end up shutting down，” he said.He compared it to shopping at “supermarkets of love” and said psychological research shows people presented with too many choices tend to make lazy and often poor decisions.The study’s authors also questioned the algorithms (算法)employed by sites such as eHarmony.com to match people based on their interests or personality—comparing it to having a real estate agent of love.While the algorithm may reduce the number of potential partners from thousands to a few， they may be as unsuitable for each other as two people meeting at random， Dr.Finkel explained， adding the chances are no better than finding a relationship by walking into any bar.“There’s no better way to figure out whether you’re a match with somebody than talking to them over a coffee or beer，” Dr.Finkel said.The phrase “lend themselves to” (Para.3)probably means ().

5. Passage TenNowadays， children heavily cling to digital devices such as computers and smart phones.Some spend up to six hours a day on their digital devices.They can be playing games online with people elsewhere， updating their status on social media， texting friends， or looking for the latest apps to download to their computers or smart phones.This worried Martin Strott.He is the headmaster of the Old Hall School in Wellington， England.He was so concerned that he challenged his students to take part in a week of (“digital detox”)， a program to reduce their reliance on digital devices.Mr.Strott told the local newspaper， the Shropshire Star， that too much screen time would affect the development of their social skills.At another interview with a magazine， he mentioned that this over-reliance on digital devices “takes away family time and reduces their chances of face-to-face communication”.The parents are happy with the program.But what about the children? Nine-year-old Fred usually spends around two hours on his digital devices at home after school and around 12 hours on weekends.For him， the digital detox experience was “really hard”.He said that he had been engaged in many interesting outdoor activities organized by the headmaster， but still missed his phone and online games.The idea of keeping children away from their digital devices for a while to prevent too much dependence on them is not particularly new.There have been similar practices in the United States.But are they effective in the long run? According to Mr.Strott， even if kids go back to their digital devices， the hope is that at least they will think about how they will use their time.What is the passage mainly about?

34.By the time we got to the cinema the film ()for half an hour.

A. 　has begun

B. 　had begun

C. 　has been on

D. 　had been on

2.I＇m very sorry to have ()you with so many questions on such an occasion.

A. 　interfered

B. 　offended

C. 　impressed

D. 　bothered

18.()you are leaving tomorrow， we can eat dinner together tonight.

A. 　For

B. 　Since

C. 　Before

D. 　While

4. Passage Thirty-TwoHave you ever heard of a pawpaw (木瓜)? If not， do not feel bad.Many Americans do not know of the fruit， although it is native to the U.S.Once， however， it was one of the most popular fruits in North America.Happily， those who love the pawpaw are trying to return it to its former position in American foods.A pawpaw is a tropical fruit that used to be grown along the East Coast from New York to Florida and all over the eastern U.S.At one time， it could be found as far west as Nebraska.The pawpaw was an important food for Native Americans and even early European settlers.Pawpaws reportedly were a favorite treat of George Washington， the first U.S.president， who especially liked them cold.Thomas Jefferson， the third U.S.president， was also a fan of the fruit.He planted pawpaws at his home in Virginia.He also sent pawpaw seeds to his friends in France.American explorers Lewis and Clark wrote in their journals about the pawpaw.The pawpaw is difficult to be sold commercially.The fruit requires a very special environment—low， wet areas that sometimes flood.It has a very short harvest season， from two to three weeks in September and October.In addition， the fruit is good to eat for only two to three days after harvesting.This makes it hard to sell anywhere distant from the pawpaw tree it comes from.Planters are again growing pawpaw trees and harvesting the fruit.In several states farmers have organized “pawpaw festivals” to reintroduce people to food.At such a festival in Maryland recently， farmers displayed different products made with pawpaws， like pawpaw jams， pies， ice-cream and beer.It is difficult to sell the pawpaw on a large scale for the following reasons EXCEPT that the fruit ().

15.She cooked the meat for a long time so as to make it ()enough to eat.

A. 　mild

B. 　slight

C. 　light

D. 　tender

1. Passage Twenty-NineHow can we get rid of garbage (垃圾)? Do we have enough energy sources to meet our future energy needs? These are two important questions that many people are asking today.Some people think that man might be able to solve both problems at the same time.They suggest using garbage as an energy source， and at the same time it can save the land to hold garbage.For a long time， people buried garbage or dumped (倾倒)it on empty land.Now， empty land is scarce.But more and more garbage is produced each year.However， garbage can be a good fuel to use.The things in garbage do not look like coal， petroleum， or natural gas; but they are chemically similar to these fossil fuels.As we use up our fossil-fuel supplies， we might be able to use garbage as an energy source.Burning garbage is not a new idea.Some cities in Europe and the United States have been burning garbage for years.The heat that is produced by burning garbage is used to boil water.The steam that is produced is used to make electricity or to heat nearby buildings.In Paris， France， some power plants burn almost 2 million metric tons of the city’s garbage each year.The amount of energy produced is about the same as would be produced by burning almost a half million barrels of oil.Our fossil fuel supplies are limited.Burning garbage might be one kind of energy source that we can use to help meet our energy needs.This method could also reduce the amount of garbage piling up on the earth.What two problems can man solve by burning garbage?

39.I apologize for ()my promise.

A. 　not having kept

B. 　being kept

C. 　not to have kept

D. 　having not kept

3. Passage NineteenA 3-year-old boy who was lost in the woods for two days is now safe at home.But Casey Hathaway told his rescuers that he was not alone in the rainy， freezing cold woods.He said he was with a friend——a bear.The child went missing on January 22 while playing with friends at his grandmother’s house in the southern state of North Carolina.When the other children returned to the house and Casey did not， the family searched the area for almost an hour before calling the police.Police formed a search and rescue team to look for the young boy in the nearby woods.But two days went by and still——no Casey.The woods of North Carolina are home to many black bears， like this one.It seems one of them helped a little boy while he was lost in the woods.Then on January 24， someone called the police saying they heard a child crying in the woods.Police followed up on the information and found Casey at about 9:30 that night.They pulled him out of some briar (荆棘).He was in good health.Police Officer Chip Hughes said that Casey did not say how he was able to survive in the woods for two days in the cloud， rainy weather， but that “he did say he had a friend in the woods that was a bear that was with him.”Hundreds of people helped in the search and rescue efforts， including some 600 volunteers， federal police and members of the military.Hughes told reporters that at no point did he think Casey had been kidnapped (绑架).Doctors at Carolina East Medical Center treated Casey for minor injuries.He was then released to his family on January 25.After receiving the call， the police ().