题目
题型：同步题难度：来源：
were found inside the cave, and I have been examining them. The C14 test shows that they are
about 12,000 years old."
"What is the C14 test?" I asked. "It"s a way of finding the age of some things that had been
done long ago. The "C" means carbon and carbon is found in al
l living things. It is also found inthe remains of things that lived and died thousands or millions of years ago. Plants and animals
take carb
on into their bodies from the air. It stays in their remains.""Well, there are two kinds of carbon, called carbon 12(C12) and carbon 14 (C14). Both are
taken in together, but in living things C12 is one trillion (1012) times more plentiful (大量的) than
C14. The two kinds are different in one important aspect."
"C14 is radioactive:it gives out rays of energy at a fixed frequency (频率). As it does so, it
changes to C12 in 5,600 years. Then in the next 5,600 years, half of the remaining C14 becomes
C12 and so on. We say that C14 has a half-life (半衰期) of 5,600 years."
"You must have found some C14 in these bones, then," I said.
"Yes, I did. But the C12 is now four million times more plentiful. About a quarter of the C14
is left. That means nearly enough, that two half-lives have passed." The doctor picked up one of the
brown toe bones. "It"s 12,000 years since this toe was broken. Perhaps the man was playing football
outside-with no boots on."
B. dead bodies
C. newly-found ancient places
D. caves where ancient people lived
B. and we all have some in us
C. found only in bones
D. but it disappears after 5,600 years
B. old bones have a half-life
C. radioactive materials have a half-life
D. a living thing has a half-life
答案
核心考点
试题【阅读理解。 The doctor pointed to some bones on his desk. "They are a man"s foot b】；主要考察你对题材分类等知识点的理解。[详细]
举一反三
education, according to new research.
Dr. Helen Lees, from Stirling University"s school of education, says that "enforced(强制的)silence
" is seen as a punishment and often acts to suppress children"s natural ability. But she says that teaching
children about the benefits of "enforced silence",--- deliberate stillness that gives them the opportunity
to focus and reflect in a stress-free environment--- can have a significant effect on pupils" concentration
and behavior.
It is the latest in a string of researches to establish a link between the classroom environment and
pupils" academic ability.
A study almost a decade ago in London found that children"s exam results were cut by as much as
a third if they were taught in noisy classrooms. Teaching unions have also called for a limit of 26℃ to
be put on classroom temperatures because teachers and pupils struggle to work in hot conditions, and
some educationalists claim that too much clutter(杂乱的东西)on classroom walls can prevent children
from concentrating.
Dr. Lees said, "When we take some research on school settings and put it all together, what we see
is that education without silence does not make much sense. In areas of better learning outcomes, better
self- confidence and well-being measures, enforced silence in a person"s life and an individual"s
education is shown throughout the relevant research to be a benefit."
Dozens of schools across Britain have already introduced periods of "reflective silence" into the
timetable.
Kevin Hogston, head of Sheringdale Primary, south London, has just introduced a minute"s silence
at the start of twice-weekly meetings in which children are taught breathing techniques and encouraged
to reflect. The school plans to introduce it into classrooms every day.
B. does not make much sense in class
C. can improve pupils" confidence
D. makes pupils more creative
B. improve
C. apply
D. reveal
B. Silence makes a great difference to pupils.
C. Clutter on the walls can help students concentrate.
D. Most schools are not satisfactory in terms of classroom temperatures.
B. Achieving silence is beneficial for people
C. Using enforced silence is effective punishment
D. Keeping quiet in class improves academic performance
parent" at all stages of a child"s life. Some parents are at their best before their children begin to speak.
Others are most successful before their children enter elementary school. Still others make their finest
contribution to older children or teenagers. Every parent can understand one stage of a child"s
development better than another. It is hard for a person to possess superior capacities throughout the
entire period of a child"s growth.
A mother might be "a good parent" from her baby"s birth until it is three; that is the period when it
needs her protection and loving care. Then the start of her child"s independence might upset and alarm
her, and she might then become less helpful for a few years. A father might be awkward and
uncomfortable with a younger child, but could turn into an excellent parent when the child is old enough
to be taught the skills of cycling, fishing and so on, or to be taken on trips. Some parents feel easier with
boys, and others with girls - and then only at certain ages or stages.
It is important for parents to understand and accept their own limitations in these matters, just as they
must accept the child"s faults of personality and limitations of talent. Otherwise, fathers and mothers will
feel guilty and blame themselves for weaknesses that may not be their faults. Much of the guilt
experienced by modern parents comes from the mistaken feeling that they ought to be all things at all
times to the child, which is clearly mistaken. In past ages, grandparents and uncles and aunts lived with
the family, and provided different kinds of support; in our present "nuclear" family, too many roles are
demanded of the two parents, which they cannot possibly fulfill.
B. most parents are only good at helping older children or teenagers
C. parents are usually at their best before their children go to school
D. parents do not realize they cannot perform equally well through a child"s growth
B. they realize their weaknesses in raising children
C. their grandfathers and uncles and aunts don"t live with them
D. they don"t know their limitations in raising children
B. they dislike the support that other family members give to their children
C. they do not always have the help of other family members in child-raising
D. they no longer regard grandparents, uncles and aunts as good educators of their children
Six-month-old babies are strictly limited in what they can remember about the objects they
see in the world. If you hide several objects from babies, they will only remember one of those
objects. But a new study, which was published in an issue of Psychological Science, a journal
of the Association for Psychological Science, finds that when babies “forget” about an object,
not all is lost. Researchers used to think that babies less than two years old did not understand
than an object continues to exist when it is not in the baby’s view. But in the mid-1980s, new
ways of doing experiments with babies found that they do, if fact, know that objects don’t
disappear when they are not looking at them- a concept know as object permanence. But it
was still unknown what babies needed to remember about objects in order to remember their
existence.
Now Melissa Kibbe, of Johns Hopkins University, and Alan Leslie, of Rutgers University, are
working to figure out exactly what it is that babies remember about objects. For the new study,
they showed six-month-old babies two objects, a disk and a triangle. Then they hid the objects
behind small screens, first one shape, then the other. Earlier research has shown that young babies
can remember what was hidden most recently, but have more trouble remembering the first object
that was hidden. Once the shapes were hidden, they lifted the screen in front of the first object.
Sometimes they showed babies the shape that was hidden there originally, but sometimes it was
the other shape, and sometimes the object had vanished completely.
Psychologists measure how long babies look at something to see how surprised they are. In
Kibbe and Leslie’s study, babies weren’t particularly surprised to see that the shape hidden behind
the screen had changed, for example, from a triangle to a disk. But if the object was gone altogether,
the babies looked significantly longer, indicating surprise at an unexpected outcome. “This shows
that even though babies don’t remember the shape of the object, they know that it should continue
to exist,” Kibbe says. “They remember the object without remembering the features that identify that
object.”
This helps explain how the young brain processes information about objects, Leslie says. He
thinks the brain has a structure that acts like a kind of pointer, a mental finger that points at an object.
B. Why babies were interested in what was hidden.
C. What made babies remember objects’ existence.
D. Whether babies can remember what was hidden first.
B. forgotten
C. discovered
D. hidden
B. how the young brain deals with information about objects
C. whether babies were surprised when they found the objects disappeared
D. why babies less than two years did not understand a hidden object still existed
B. What babies remember about objects
C. A new study on psychology
D. All remembered isn’t lost
middle schools and high schools.
78% of the schools have at least one fastfood place within less than a half mile or about a 10minute
walk.
Half the area"s schools have a fastfood restaurant a third of a mile or closer, about a fiveminute walk.
In some cases, the restaurant is right next door or across the street.
There are three to four times as many fastfood restaurants within less than a mile of schools than they
would be expected.
Most public and private schools in Chicago are only a fiveto10minute walk from at least one fastfood
restaurant. The city is facing the same problem like other areas. Children and teens are surrounded by
unhealthy options.
Students can pick up fast foods, including hamburgers, French fries, fried chicken and doughnuts, on
the way to and from school. Some high school students can go off campus at lunchtime to eat it. "Five
days a week we send children to an environment where there"s an abundance of highcalorie,
lownutritionalquality, inexpensive food," says Bryn Austin.
The research comes from growing concerns that American schoolchildren are gaining weight. About
31% of kids aged 6 to 19 are overweight or at risk of becoming so. On days when kids eat fast food,
they have more calories, more fat, more sugar and fewer fruits and vegetables than on other days.
Kelly Brownell from Yale University said, "Just like there are drugfree zones around schools, there
should be zones around schools that are free of junk food, including fastfood restaurants, minimarkets
and gas stations that sell food inside."
B. fastfood restaurants are doing harm to students
C. there are many fastfood restaurants around schools
D. fastfood restaurants around schools have been a problem
B. high in calories and low in nutrition
C. inexpensive for students to buy
D. high in nutrition and low in calories
B. set up zones free of junk food around schools
C. charge fastfood restaurants around school
D. close all the gas stations around schools
B. Zones Free of Junk Food in Need Around Schools
C. FastFood Restaurants Crowd Chicago Schools
D. FastFood Restaurants Should Not Be Allowed
is only mildly annoying. On a cellphone, it could make you want to skip the purchase entirely.
This is why investors, startups (初创企业) and major corporations are pouring money into
services that make it easier to use cellphones to buy goods and transfer money. The aim is to turn
phones into virtual credit cards or checkbooks, enabling the kind of clickandbuy commerce and online
banking that people have come to expect on their PCs. But shrinking down (缩小) those services
presents serious challenges.
The services must work on many different phones and through many cellphone service providers,
which usually control the billing relationships with customers. That adds complexity to the already tricky
business of safely and securely transferring funds among financial institutions and merchants.
Mobile payment systems have been tried before, with only modest success. Driving a new flurry
(一阵兴奋) of deal making, industry analysts and executives say, is the success of the iPhone,
BlackBerry and other sophisticated (尖端的) devices. These phones make complex interactions easier.
Now the race is on to develop new payment systems-and to get several percentage points in fees
from each transaction. They"re seeing that returns could be so huge. Obopay, a startup that lets people
transmit money to one another via text message, raised $ 35 million from Nokia"s investment. Also, a
mobile payments startup called Boku announced that it had received $ 13 million in venture capital
financing.
When people can use their phone numbers to make a purchase, they are 10 times as likely to follow
through on a transaction as when they have to type in credit card and billing information, said David
Marcus, chief executive of a startup called Zong.
Mobile payment companies also need to get cooperation from merchants, which must add a payment
option to their mobile sites or applications.
But the potential opportunity to get fees from the growing number of mobile transactions is too
__juicy__to__pass__up,__despite the risks, said an analyst with IDC Financial Insights, a market
research company.
through cellphones instead of PCs.
B. two
C. three
D. four
B. convenient
C. troublesome
D. impossible
B. Too difficult to seize.
C. Too heavy to lift.
D. Too unsafe to handle.
B. The Great Risks on Payments via Cellphone
C. How to Deal with Payments via Cellphone
D. Investors Bet on Payments via Cellphone
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