相关试题
Most people findrejectionhard to accept.
A: excuse
B: client
C:destiny
D: refusal
共用题干
Avalanche and Its Safety
An avalanche is a sudden and rapid flow of snow,often mixed with air and water,down a mountainside .Avalanches are______(51)the biggest dangers in the mountains for both life and property.
All avalanches are caused by an over-burden of material,typically snowpack,that is too massive and unstable for the slope______(52)supports it. Determining the critical load,the amount of over-burden which is______(53)to cause an avalanche，______（54)a complex task involving the evaluation of a number of factors.
Terrain slopes flatter than 25 degrees or steeper than 60 degrees typically have a low ______(55)of avalanche .Snow does not______(56)significantly on steep slopes;also, snow does not______(57)easily on flat slopes.Human-triggered avalanches have the greatest incidence when the snow's angle of rest is______(58)35 and 45 degrees;the critical angle, the angle at which the human incidence of avalanches is greatest,is 38 degrees.The rule of thumb is:A slope that is______(59)enough to hold snow but steep enough to ski has the potential to generate an avalanche,regardless of the angle.Additionally,avalanche risk increases with ______(60);that is,the more a slope is disturbed by skiers,the more likely it is that an avalanche will occur.
Due to the complexity of the subject,winter travelling in the backcountry is never 100% safe .Good avalanche safety is a continuous______(61),including route selection and examination of the snowpack,weather______(62),and human factors.Several well-known good habits can also______(63)the risk .If local authorities issue avalanche risk reports,they should be considered and all warnings should be paid______(64)to.
Never follow in the tracks of others without your own evaluations;snow conditions are almost certain to have changed since they were made .Observe the terrain and note obvious avalanche paths where plants are ______(65)or damaged .Avoid travelling below others who might trigger an avalanche.
51._________
A: among
B: on
C: at
D: with
共用题干
Electromagnetic Energy
1 White light seems to be a combination of all colors.The energy that comes from a source of light is
not limited to the kind of energy you can see.Heat is given off by a flame or an electric light.On a cloudy
day it is possible to get a sunburn even though you feel cool.Visible light and the kind of energy that produce
warmth and sunburn are examples of electromagnetic energy.
2 The sun is 93 million miles away from the earth.Yet we can use energy from the sun because elec-
tromagnetic energy travels through space.
3 Many other kinds of energy are also types of electromagnetic energy.Radio,television,and radar signals
travel from transmitters to receivers as low-energy electromagnetic waves. Infrared（红外线的）radiation is an
electromagnetic wave.When it is absorbed by matter,heat is produced.Waves of infrared and visible light
have more energy than waves of radio , television , or radar. Ultraviolet rays（紫外线）and X-rays are electro-
magnetic waves with even greater amounts of energy.Infrared radiation is used in cooking food and heating
buildings.Sunlight and electric lights are part of our requirements for normal living. Ultraviolet radiation is
useful in killing certain disease organisms.X-rays and gamma rays have so much energy that they travel right
through solid objects.They can be used to detect and treat cancer. X-rays are used in industry to find hidden
cracks in metal,and in medicine to reveal broken bones.
4 Usually we use electricity to generate electromagnetic energy.The source of most of our energy is the
sun.Heat from the sun causes water to evaporate.When the water falls to the earth as rain,some of it is
trapped behind dams and then used to operate electric generators.Other generators are powered by coal,but
the energy stored in coal came from the sun,too.
5 Until recently,the source of the tremendous amount of energy given off by the sun was a puzzle.If
the.sun depended on chemical reactions,it would have used up all its energy long ago.Experiments with
electromagnetic radiation led to the theory that mass can be converted into energy.About forty years after the
theory was proposed , nuclear energy was harnessed（利用）by man. Chemical energy comes from electron
（电子）rearrangement. Nuclear energy comes from a change in the nucleus of an atom. Compared with chemi-
cal reactions,nuclear reactions release millions of times more energy per pound of fuel.We now believe that
the sun's energy comes from the nuclear reactions in which hydrogen is changed into helium（氦）.
6 Nuclear energy is beginning to compete with coal as an economical source of power to generate elec-
tncity.It is also being used to operate engines in large ships.Scientists continue to seek new and better
methods of obtaining and using energy.
Paragraph 3_____________
A:Nuclear Reactions as the Lasting Source of the Sun's Energy
B:The Most Important Source of Energy
C:Types of Electromagnetic Energy
D:X-rays Are Used to Detect and Treat Cancer
E:Seeking New Sources of Energy
F:Nuclear Energy Is Beginning to Compete With Coal
共用题干
Women's minds work differently from men's.At least,that is what most men are convinced of. Psychologists view the subject either as a matter of frustration or a joke.Now the biologists have moved into this minefield,and some of them have found that there are real differences between the brains of men and women.But being different,they point out hurriedly,is not the same as being better or worse.
There is,however,a definite structural variation between the male and female brain.The difference is in a part of the brain that is used in the most complex intellectual processes一the link between the two halves of the brain.
The two halves are linked by a trunk line of between 200 and 300 million nerves,the corpus callosum.Scientists have found quite recently that the corpus callosum in women is always larger and probably richer in nerve fibres than it is in men.This is the first time that a structural difference has been found between the brains of women and men and it must have some significance.The question is"What?",and,if this difference exists,are there others?Research shows that present-day women think differently and behave differently from men.Are some of these differences biological and inborn,a result of evolution?We tend to think that is the influence of society that produces these differences.But could we be wrong?
Research showed that these two halves of the brain had different functions,and that the corpus callosum enabled them to work together. For most people,the left half is used for word-handling, analytical and logical activities;the right half works on pictures,patterns and forms.We need both halves working together. And the better the connections,the more harmoniously the two halves work.And,according to research findings,women have the better connections.
But it isn't all that easy to explain the actual differences between skills of men and women on this basis.In schools throughout the world girls tend to be better than boys at"language subjects" and boys better at maths and physics.If these differences correspond with the differences in the hemispheric trunk line,there is an unalterable distinction between the sexes.
We shan't know for a while,partly because we don't know of any precise relationship between abilities in school subjects and the functioning of the two halves of the brain,and we cannot understand how the two halves interact via the corpus callosum.But this striking difference must have some effect and,because the difference is in the parts of the brain involved in intellect,we should be looking for differences in intellectual processing.
According to the passage it is commonly believed that brain differences are caused by social factors.
A:Right
B:Wrong
C:Not mentioned
共用题干
Less Is More
It sounds all wrong—drilling holes in a piece of wood to make it more resistant to knocks. But it works because the energy from the blow gets distributed throughout the wood rather than fo-
cusing on one weak spot. The discovery should lead to more effective and lighter packaging mate-rials.
Carpenters have known______(51)centuries that some woods are tougher than others. Hickory,for example,was turned into axe handles and cartwheel spokes because it can absorb shocks without breaking. White oak,for example,is much more easily damaued,________(52)it is almostas dense.Julian Vincent at Bathe University and his team were convinced the wood's internal structure could explain the differences.
Many trees have tubular vessels that run_______(53)the trunk and carry water to the leav- es .In oak they are large,and arranged in narrow bands,but in hickory they are smaller,and more evenly distributed.The researchers________(54)this layout might distribute a blow's en-ergy throughout the wood, soaking up a bigger hit.To test the idea,they drilled holes 0.65 millimetres across into a block of spruce,a wood with_______(55)vessels,and found that_______(56)withstood a harder knock_______（57)when there were more than about 30 holes per square centimeter did the wood's performance drop off.
A uniform substance doesn't cope well with knocks because only a small proportion of the material is actually______( 58).All the energy from the blow goes towards breaking the material in one or two places , but often the pieces left _________( 59 ) are pristine（未经破坏的）.
But instead of the energy being concentrated in one place,the holes provide many weak spots that all absorb energy as they break,says Vincent.“You are controlling the places______(60) the wood breaks,and it can then absorb more______(61),more safely.”
The researchers believe the principle could be applied to any material—_________(62)example,to manufacture lighter and more protective packaging.It could_______(63)be used in car bumpers,crash barriers and armor for military vehicles,says Ulrike Wegst,_______(64) the Max Plank Institute for Mental Research in Stuttgart. But she emphasizes that you'd ________(65)to design the substance with the direction of force in mind.“The direction of loading is crucial,”she says.
60._________
A:.which
B: where
C: that
D:.there
