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Screen Test
1 Every year millions of women are screened with X-rays to pick up signs of breast cancer. If this
happens early enough,the disease can often be treated successfully.According to a survey published last
year,2 1 countries have screening programs.Nine of them,including Australia,Canada,the US and Spain,
screen women under 50.
2 But the medical benefits of screening these younger women are controversial,partly because the
radiation brings a small risk of inducing cancer. Also,younger women must be given higher doses of X-rays
because their breast tissue is denser.
3 Researchers at the Polytechnic University of Valencia analyzed the effect of screening more than
160,000 women at 11 local clinics.After estimating the women's cumulative dose of radiation,they used
two models to calculate the number of extra cancers this would cause.
4 The mathematical model recommended by Britain's National Radiological Protection Board
(NRP
B)predicted that the screening program would cause 36 cancers per 100,000 women,18 of them
fatal.The model preferred by the UN Scientific Committee on the Effects of Atomic Radiation led to a lower
figure of 20 cancers.
5 The researchers argue that the level of radiation-induced cancers is"not very significant"compared
to the far larger number of cancers that are discovered and treated.The Valencia program,they say,detects
between 300 and 450 cases of breast cancer in every 100,000 women screened.
6 But they point out that the risk of women contracting cancer from radiation could be reduced by
between 40 and 80 percent if screening began at 50 instead of 45,because they would be exposed to less
radiation.The results of their study,they suggest,could help"optimize the technique"for breast cancer
screening.
7 "There is a trade-off between the diagnostic benefits of breast screening and its risks," admits
Michael Clark of the NRP
B.But he warns that the study should be interpreted with caution."On the basis of
the current data,for every 10 cancers successfully detected and prevented there is a risk of causing one later
in life.That'S why radiation exposure should be minimized in any screening program."
Delaying the age at which screening starts may_________.
A.be costly
B.harmful
C.save a life
D.still open to debate
E.reduce the risk of radiation triggering a cancer
F.reduced to the minimum
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Earthquake
1.Every year earthquakes are responsible for a large number of deaths and a vast amount of destruction in various parts of the world.Most of these damaging earthquakes occur either in a narrow belt which surrounds the Pacific Ocean or in a line which extends from Burma to the Alps in Europe. Some of the destruction is directly caused by the quake itself. An example of this is the collapse of buildings as a result of the quake itself. Other damage results from landslides or major fires which are initiated by the quake.
2.There are about a million quakes a year. Fortunately,however,not all of them are destructive.The intensity of an earthquake is measured on the Richter Scale,which goes from 0 upward. The highest scale recorded to date is 8.9.Major damage generally occurs from quakes ranging upwards from 6.0.
3.The actual cause of the quake itself is the breaking of rocks at or below the earth's surface. This is produced by pressure which scientists believe may be due to a number of reasons, two of which are the expansion and contraction of the earth's crust and continental drift.
4.In order to limit the damage and to prevent some of the suffering resulting from earthquakes, scientists are working on ways to enable accurate prediction.Special instruments are used to help people record,for example,shaking of the earth.Scientists are trying to find methods that will enable them to indicate the exact time,location and size of an earthquake.
5.Certain phenomena have been observed which are believed to be signs of imminent earth-quakes.These include strange behaviors of some animals,the changes in the content of mineral water,etc.The magnetic properties of rocks may also display special pattern before major earthquakes happen.
Earthquakes can be predicted by observing__________.
A.by the quake itself
B.not be prevented
C.to cause damage of property and loss of lives
D.of a possible earthquake
E.the unusual behaviors of some animals
F.the strange behaviors of human beings
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In every cultivated languages there are two great classes of words which taken together,comprise the whole vocabulary.First,there are those words_________(51)which we become acquainted in daily conversation,which we learn,that is to say,from the_________(52)of our own family and from our familiar associates,and which we should know and use_________(53)we could not read or write.They__________(54)the common things of life,and are the stock in trade of all who use the language.Such words may be called"popular",since they belong to the people___________ (55)and are not the exclusive_______(56)of a limited class. On the other hand,our language ___________(57)a multitude of words which are comparatively_________(58)used in ordinary conversation.Their meanings are known to every educated person,but there is little_________(59)to use them at home or in the market-place. Our________ (60) acquaintance with them comes not from our mother's________(61)or from the talk of our schoolmates,________(62)from books that we read,lectures that we_________(63),or the more formal conversation of highly educated speakers who are discussing some particular topic in a style appropriately elevated above the habitual ________(64)of everyday life.Such words are called "learned" ,and the________(65)between them and the "popular" words is of great importance to a right understanding of linguistic process.
_________(64)
A.border
B.link
C.degree
D.extent
