相关试题
共用题干
Where Has the Salt Come from?
Every now and then,we meet a fact about our earth that makes us feel strange and no
answer for the fact has yet been found.Such a fact is the existence of salt in the oceans.
How did it get there?
We simply do not know how the salt got into the ocean!We do know,of course,that
salt is water-soluble,and so passes into the oceans with rainwater.The salt of the earth's
surface is constantly being dissolved（溶解）and is passing into the ocean.
But we do not know whether this can explain the huge quantity of salt in oceans.If all
the oceans were dried up,enough salt would be left to build a wall 180 miles high and a
mile thick. Such a wall would reach once around the world at the Equator（赤道）!
The common salt that we all use is produced from seawater or the water of salt lakes,
from salt springs（源泉）and from deposits of rock salt. The concentration（浓度）of salt in
seawater ranges from about three percent to three-and-one-half percent. The Dead Sea,
which covers an area of about 340 square miles,contains about 11,600,000,000 tons of
salt!
On the average, a gallon（加仑）of seawater contains about a quarter of a pound of
salt.The beds of rock salt that are found in various parts of the world were all originally
formed by the evaporation（蒸发）of seawater millions of years ago. It is believed that the
thick rock-salt deposits were formed after about nine-tenth of theY volume of seawater had
been evaporated.
Most commercial salt is obtained from rock salt.The usual method is to drill wells（井）
down to the salt beds. Pure water is pumped down（抽进去）through a pipe. The water
dissolves the salt and it is forced through another pipe up to the surface.
We have not fully understood how salt got into the ocean.
A:Right
B:Wrong
C:Not mentioned
共用题干
The iPad
1 The iPad is a tablet computer（平板电脑）designed and developed by Apple. It is par-ticularly marketed as a platform for audio and visual media such as books,periodicals（期刊）,movies,music,and games,as well as web content. At about 1 .5 pounds(680 grams), its size and weight are between those of most contemporary smartphones and laptop comput-ers.Apple released the iPad in April 2010,and sold 3 million of the devices in 80 days.
2 The iPad runs the same operating system as iPod Touch and iPhone. It can run its own applications as well as ones developed for iPhone. Without modification,it will only run pro-grams approved by Apple and distributed via its online store.
3 Like iPhone and iPod Touch,the iPad is controlled by a multitouch display一a break from most previous tablet computers, which uses a pressure-triggered stylus（触控笔）.The iPad uses a Wi-Fi data connection to browse（浏览）the Internet, load and stream media, and install software. Some models also have a 3G wireless data connection which can connect to GSM 3G data networks. The devices is managed and synchronized（同步）by iTunes on a per-sonal computer via USB cable.
4 An iPad has different features and applications one can use to execute different and in-teresting things. There are lots of iPad applications that the owner can use to enhance the way they communicate. Some of these are how to use social networking sites and other online options.One of the most common uses is for e-mail services. iPad applications like Markdown Mail allow the adoption of specific and particular options. They enable the owner to personal-ize their email accounts.
5 While the iPad is mostly used by consumers it also has been taken up by business us-ers. Some companies are adopting iPads in their business offices by distributing or making available iPads to employees.Examples of uses in the workplace include lawyers responding to clients,medical professionals accessing health records during patient exams,and manag-ers approving employee requests.A survey by Frost Sullivan shows that iPad usage in work-places is linked to the goals of increased employees productivity,reduced paperwork,and in-creased revenue.
Paragraph 2______
A: Online Stores
B: Differences from iPhone
C: Display and Data Connection
D: Business Usage
E: Features and Applications
F: Operating System
共用题干
Drying Ways for Food
1.Centuries ago,man discovered that removing moisture from food helps to preserve it,and that the easiest way to do this is to expose the food to sun and wind.In this way the North American Indians produce pemmican(dried meat ground into powder and made into cakes),the Scandinavians make stockfish and the Arabs dried dates and"apricot leather".
2.All foods including water,cabbage and other leaf vegetables contain as much as 93%water, potatoes and other root vegetables 80%,lean meat 75%and fish,anything from 20%to 60%,depending on how fatty it is.If this water is removed,the activity of the bacteria which causes food to go bad is checked.
3.Fruit is sun-dried in Asia Minor,Greece,Spain and other Mediterranean countries,and also in California,South Africa and Australia. The methods used vary, but in general,the fruit is spread out on trays in drying yards in the hot sun.In order to prevent darkening,pears,peaches and apricots are exposed to the fumes of burning sulfur before drying. Plums,for making prunes, and certain varieties of grapes for making raisins and currants,are dipped in an alkaline solution in order to crack the skins of the fruit slightly and remove their wax coating,so as to increase the rate of drying.
4.Nowadays most foods are dried mechanically.The conventional method of such dehydration is to put food in chambers through which hot air is blown at temperatures of about 110℃at entry and to about 43℃at exit. This is the usual method for drying such things as vegetables,minced meat, and fish.
5.Liquids such as milk,coffee,tea,soups and eggs may be dried by pouring them over a heated steel cylinder,by spraying them into a chamber through which a current of hot air passes.In the first case,the dried material is scraped off the roller as a thin film which is then broken up into small,though still relatively coarse flakes.In the second process,it falls to the bottom of the chamber as a fine powder. Where recognizable pieces of meat and vegetables are required,as in soup, the ingredients are dried separately and then mixed.
6.Dried foods take up less room and weigh less than the same food packed in cans or frozen, and they do not need to be stored in special conditions.For these reasons they are invaluable to the climbers,explorers and soldiers in battle,who have little storage space.They are also popular with housewives because it takes so little time to cook them.Usually it is just a case of replacing the dried-out moisture with boiling water.
Paragraph 5______
A:Drying Fruit in the Traditional Way.
B:Food Drying Histrory.
C:Water in Food.
D:Drying of Liquid Food.
E:Advantages of Dry Food.
F: Mechanical Food Dehydration.
共用题干
第一篇
Walking to Exercise the Brain
Do you think sitting and studying all the time will improve your grades?Think again.Getting some exer-
cise may help,too.
New research with old people suggests that taking regular walks helps them pay attention better than if
they didn't exercise.
Previous research had shown that mice learn,remember,and pay attention better after a few weeks of
working out on a running wheel.Mice that exercise have greater blood flow to the brain than those who don't.
Their brain cells also make more connections.
Neuroscientists（神经科学家）from the University of Illinois at Urbana Champaign wanted to find out if
the same thing is true for people.First,they measured the physical fitness of 41 adults,ages 58 to 77,after
each person walked 1 mile.Then,participants looked at arrows on a computer screen and had to use computer
keys to show which way one particular arrow was pointing.
Adults who were physically fit were faster at the arrow task,and their answers were just as accurate as
their less-fit peers,the researchers found.The fitter participants also had more blood flow to a part of their
brain responsible for paying attention and making decisions.
In a second study , 15 elderly people who completed a 6-month aerobic-training（有氧运动）course were
faster at attention tasks compared with 14 seniors who just did stretching and toning exercises（韵律操）for
the same amount of time.
So,even going for a walk every 2 or 3 days for just 10 to 45 minutes can help.That should be good news
for the elderly.
The effects of exercising on the brains of younger people haven't been studied yet. Still,it can't hurt to
take occasional breaks and go for a walk or run around with friends.Whatever you do,though,don't try to
read and walk at the same time.You could end up hurting yourself!
The first study on 41 elderly people found______________.
A:the less-fit participants did arrow tasks faster
B:the fitter participants did arrow tasks faster
C:the less-fit participants gave more accurate answers
D:the fitter participants gave more accurate answers
共用题干
Germs（细菌）on Banknotes
People in different countries use different types of money:yuan in China,pesos in Mexico,pounds in the United Kingdom,dollars in the United States,Australia and New Zeal-and. They may use different currencies,but these countries,and probably all countries,still have one thing in______(1):germs on the banknotes.
Scientists have been studying the germs on money for well over 100 years. At the turn of the 20th______(2),some researchers began to suspect that germs living on money could spread disease.
Most studies of germy money have looked at the germs on the currency______(3)one country. In a new study,Frank Vriesekoop and other researchers compared the germ populations found on bills of different______(4).
Vriesekoop is a microbiologist at the University of Ballarat in Australia. He led the stud-y,which compared the germ populations found on money______(5)from 10 nations. The scientists studied 1,280 banknotes in total;all came from places where people buy food,like supermarkets,street vendors and cafes,______(6)those businesses often rely on cash.
Overall,the Australian dollars hosted the fewest live bacteria一no more than 10 per square centimeter. Chinese yuan had the______(7）about 100 per square centimeter. Most of the germs on money probably would not cause harm.
What we call“paper money”_________(8)isn't made from paper. The U. S. dollar,for ex- ample,is printed on fabric that is mostly cotton. Different countries may use different______(9)to print their money. Some of the currencies studied by Vriesekoop and his team,such as the American dollar,were made from cotton. Others were made from polymers.
The three______(10)with the lowest numbers of bacteria were all printed on poly-mers. They included the Australian dollar,the New Zealand dollar and some Mexican pesos.
The______(11)currencies were printed on fabric made mostly of cotton. Fewer germs lived on the polymer notes. This______(12)suggests that germs have a harder time staying alive on polymer surfaces. Scientists need to do more studies to understand______(13)germs live on, mon-ey—and whether or not we need to be concerned. Vriesekoop is now starting a study that will______(14)the amounts of time bacteria can stay alive on different types of bills.
Whatever Vriesekoop finds,the fact remains:Paper money______(15)germs. We should wash our hands after touching it;After all,you never know where your money's been. Or what's living on it.
6._________
A: because
B: though
C: so
D: when
