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Against the assumption that forest fires in Alaska, Canada and Siberia warm the climate, scientists have discovered that cooling may occur in areas where burnt trees allow more snow to mirror more sunlight into space.
This finding suggests that taking steps to prevent northern forest fires to limit the release of greenhouse gases may warm the climate in northern regions. Usually large fires destroyed forests in these areas over the past decade. Scientists predict that with climate warming, fires may occur more frequently over next several centuries as a result of a longer fire season. Sunlight taken in by the earth tends to cause warming, while heat mirrored back into space tends to cause cooling.
This is the first study to analyze all aspects of how northern fires influence climate. Earlier studies by other scientists have suggested that fire in northern regions speed up climate warming because greenhouse gases from burning trees and plants are released into the atmosphere and thus trap heat.
Scientists found that right after the fire, large amounts of greenhouse gases entered the atmosphere and caused warming. Ozone(臭氧)levels increased, and ash from the fire fell on far-off sea ice, darkening the surface and causing more radiation from the sun to be taken in. The following spring, however, the land within the area of the fire was brighter than before the fire, because fewer trees covered the ground. Snow on the ground mirrored more sunlight back into space, leading to cooling.
“We need to find out all possible ways to reduce the growth of greenhouse gases in the atmosphere.” Scientists tracked the change in amount of radiation entering and leaving the climate system as a result of the fire, and found a measurement closely related to the global air temperature. Typically, fire in northern regions occurs in the same area every 80 to 150 years. Scientists, however, found that when fire occurs more frequently, more radiation is lost from the earth and cooling results. Specifically, they determined when fire returns 20 years earlier than predicated, 0.5 watts per square meter of area burned are soaked up by the earth from greenhouse gases, but 0.9 watts per square meter will be sent back into space. The net effect is cooling. Watts are used to measure the rate at which energy is gained or lost from the earth.
小题1:According to the new findings, taking steps to prevent northern forest fires may _______.
A.result in a warming climate
B.cause the forest fires to occur more frequently
C.lead to a longer fire season
D.protect the forests and the environment there
小题2:Earlier studies about northern forest fires ________.
A.analyze all aspects of how northern fires influence climate
B.indicate that forest fires will pollute the atmosphere
C.suggest that people should take measures to protect environment
D.suggest that the fires will speed up climate warming
小题3:The underlined phrase “soaked up” in the last paragraph most probably means ________.
A.releasedB.absorbedC.createdD.disturbed
小题4: From the text we can draw a conclusion that forest fires in Alaska, Canada and Siberia may ______.
A.warm the climate as the assumption goes
B.allow more snow to reflect more sunlight into space and thus cool the climate
C.destroy large areas of forests and pollute the far-off sea ice
D.help to gain more energy rather than release more energy .

答案

小题1:A
小题2:D
小题3:B
小题4:B
解析

核心考点
试题【 Against the assumption that forest fires in Alaska, Canada and Siberia warm the】;主要考察你对题材分类等知识点的理解。[详细]
举一反三

  “Helping survivors (生还者) of the earthquake and killer waves in the Indian Ocean last week is a race against time” says Kofi Annan , the United Nations secretary-general .
The concern about offers of international aid is based on history. Since we are social beings, the quality of our lives depends in large measure on our interpersonal relationships. One strength of the human condition is our aim to give and receive support from one another under stressful surroundings. Social support consists of the exchange of resources among people based on their interpersonal ties.
Those of us with strong support systems appear betterable to deal with major life changes and daily problems. People with strong social ties live longer and have better health than those without such ties. Studies over a range of illnesses, from depression to heart disease, show that the presence of social support helps people prevent illness, and the absence of such support makes poor health more likely.
Social support cushions stress in a number of ways. First, friends, relatives, and co-workers may let us know that they value us. Our self-respect is strengthened when we are popular with others despite our faults and difficulties. Second, other people often provide us with informational support. They help us to notice and understand our problems and find solutions to them. Third, we typically find social companionship supportive. Engaging in leisure-time activities with others helps us to meet our social needs while at the same time distracting(转移...注意力)us from our worries and troubles. Finally, other people may give us instrumental support: a financial aid, material resources, and needed services -- that reduces stress by helping us deal with our problems.
59. Research shows that people"s physical and mental health _______.
A. depends on the social welfare (福利)systems which support them
B. has much to do with the amount of support they get from others
C. depends on their ability to deal with daily worries and troubles
D. is closely related to their strength for dealing with major changes in their lives
60. The underlined word" cushions" in Para.3 means _______.
A. adds up to                                  B. does away with
C. reduce the effect of                D. depends on
61. Helping a sick neighbor with some repair work is an example of _______.
A. instrumental support                     B. informational support
C. social companionship             D. the strengthening of self-respect
62. Social companionship is very important because _______.
A. it helps strengthen our ties with relatives
B. it enables us to get rid of our faults and mistakes
C. it makes our leisure-time activities more enjoyable
D. it draws our attention away from our worries and troubles
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Natural ways of keeping time


In ancient times, people had to use the sun and the moon to tell time. They got up when the sun came up and worked in the fields until the sun went down.
Man-made things
The sand clock is made of two glass balls joined by a narrow neck. The top ball was filled with sand. The sand slowly moved through the neck into the bottom ball. People knew how much time had passed when all the sand had fallen to the bottom ball.
People also made the water clock. They made a small hole near the bottom of a pot. Then they filled the pot with water. Markings inside the pot showed how much time passed as the water dripped (滴) out of the hole.
Nature’s Clocks in Living Things
◆Animals’ Body Clock
Animals do not need clocks to know time. They have a way of telling time by their bodies. Birds know when to fly to warmer places before winter. Some animals know when to keep more food for the cold winter months. Some fish know when it is time to move up the river and lay eggs.
◆Plants have their own clocks
Plants also have their own clocks to keep time. Plants know when to open flow­ers or when to drop their leaves.
◆The Body Clock in Human Beings
People also have their own body clocks. When we get used to our lives, our body clocks can be very accurate (准确的). It can tell us when it is time to wake up. It can also tell us when to eat or to go to sleep.
小题1:How could an ancient farmer know when to go back home in the daytime?
A.By looking at the moon.B.By looking at the stars.
C.By looking at the sun.D.By feeling whether tired or not.
小题2: How many kinds of living things with nature’s clocks are mentioned here?
A.2.B.3.C.5D.6.
小题3:From the passage, we know what man-made things have in common is that_______.
A.both of them have a hole.B.both of them are designed with glass balls.
C.both of them can be used only once.D.both of them tell time in the same way

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Normally a student must attend a certain number of courses in order to graduate, and each course which he attends gives him a credit (学分) which he may count towards a degree. In many American universities the total work for a degree consists of thirty-six courses each lasting for one semester (学期). A typical course consists of three classes per week for fifteen weeks; while attending a university a student will probably take four or five courses during each semester. Normally a student would expect to take four years attending two semesters each year. It is possible to spread the period of work for the degree over a longer period. It is also possible for a student to move between one university and another during his degree course, though this is not in fact done as a regular practice.
For every course that he follows, a student is given a grade, which is recorded, and the record is available for the student to show to prospective(预期的) employers. All this imposes a constant pressure and strain of work, but in spite of this some students still find time for great activity in student affairs. Elections to positions in student organizations arouse much enthusiasm (热情). The effective work of maintaining discipline is usually performed by students who advise the academic authorities (权威). Any student who is thought to have broken rules, for example, by cheating has to appear before a student court. With the enormous numbers of students, the operation of the system does involve a certain amount of activity. A student who has held one of these positions of authority is much respected and it will be of benefit to him later in his career.
72. Normally a student would at least attend ______ classes per week.
A. 36      B. 12     C. 20       D.15
73. According to the first passage an American student is allowed ______.
A. to live in a different university
B. to take a particular course in a different university
C. to live at home and drive to classes
D. to get two degrees from two different universities
74. American students are usually under pressure of work because ______.
A. their academic performance will affect their future careers
B. they are heavily involved in student affairs
C. they have to observe university discipline
D. they want to run for positions of authoring
75. Some students are enthusiastic for positions in student organizations probably because_____.
A. they hate the constant pressure and strain of their study
B. they will then be able to stay longer in the university
C. such positions help them get better jobs
D. such positions are usually well paid
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Have you ever tried to draw a straight line, only to find it turns out all wrong? Or, have you ever wanted to show ___36___ at a party and found the song you’d practiced so many times suddenly__37_ more difficult? I’ve had both these__38___. As a senior student, I have to ___39__ many exams. Each time, I think, “ I__40___ fail this time,’’ but I get a low mark. Don’t be surprised---it’s not __41___ I don’t try, do enough preparation, __42__ take it seriously. On the contrary, it is because I give it too _43__ attention. The thought “ I must pass” makes me taste the terrible flavor of failure.
I often___44___ to my friends, “ Don’t be too hard ___45____ yourself.” However, when I __46___ my own goals, I do not listen to my own advice. So why not ___47__ this crazy thought of achieving the best? Just face the problem__48____before you with a calm mind, work and you will succeed.
In my opinion, __49___ a calm state of mind is a skill for life. People__50__ want to succeed realizing this is of __51______ importance. So __52___ time you’re trying to draw a straight line or ___53___ a performance, tell yourself, “ If I can just do it _54___ than last time, it’s a success.” Keep a calm state of mind, and you will be happy __55____you succeed or fail.
小题1:
A.aroundB.offC.outD.in
小题2:
A.becameB.becomeC.becomingD.becomes
小题3:
A.experiencesB.experienceC.times D.difficulties
小题4:
A.enterB.makeC.takeD.join
小题5:
A.won’tB. can C.needD.needn’t
小题6:
A.because ofB./C.thereforeD.because
小题7:
A.andB.orC.butD.nor
小题8:
A.manyB.fewC.littleD.much
小题9:
A.sayB.adviseC.tellD.encourage
小题10:
A.offB.onC.toD.for
小题11:
A.giveB.holdC.buildD.set
小题12: A. throw away      B. get away         C. take up         D push off
小题13:
A.lieB.liesC.lyingD.laying
小题14:
A.keepingB.stayingC.remainingD.making
小题15:
A.whomB.whichC.whoD./
小题16: A no                B. little         C. very           D. great
小题17:
A.lastB.the lastC.nextD.the next
小题18:A. put on             B play on                C. give on         D show on
小题19:
A.bestB.betterC.goodD.well
小题20:
A.ifB.eitherC.neitherD.whether

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The exact number of English words is not known. The large dictionaries have over half a million entries, but many of these are compound words (schoolroom, sugar bowl) or different derivatives of the same word (rare—rarely, rarefy), and a good many are obsolete words to help us read older literature. Dictionaries do not attempt to cover completely words that we can draw on: the informal vocabulary, especially slang, localism, the terms of various occupations and professions; words use only occasionally by scientists and specialists in many fields; foreign words borrowed for use in English; or many new words or new senses of words that come into use every year and that may or may not be used long enough to warrant being included. It would be conservative to say that there are over a million English words that any of us might meet in our listening and reading and that we may draw on in our speaking and writing.
Professor Seashore concluded that firstgraders enter school with at least 2,000 words and add 5,000 each year so that they leave high school with at least 80,000. These figures are for recognition vocabulary, the words we understand when we read or hear them. Our active vocabulary, the words we use in speaking and writing, is considerably smaller.
You cannot always produce a word exactly when you want it. But consciously using the words you recognize in reading will help get them into your active vocabulary. Occasionally in your reading pay particular attention to these words, especially when the subject is one that you might well write or talk about. Underline or make a list of words that you feel a need for and look up the less familiar ones in a dictionary. And then before very long find a way to use some of them.
Once you know how they are pronounced and what they stand for, you can safely use them.
46. In the author´s estimation, there are ____ words in English.
A. more than half a million                B. at least 24,000
C. at least 80,000                       D. more than a million
47. The word “obsolete” most probably means ____.
A. no longer in use  B. profound   C. colorful or amusing   D. common
48. One´s recognition vocabulary is ____.
A. less often used than his active vocabulary
B. smaller than his active vocabulary
C. as large as his active vocabulary
D. much larger than his active vocabulary
49. The author does not suggest getting recognition vocabulary into active vocabulary by ____.
A. making a list of words you need and looking up the new ones in a dictionary
B. everyday spending half an hour study the dictionary
C. consciously using the words you recognize in reading
D. trying to use the words you recognize
50. From this passage we learn that ____.
A. dictionaries completely cover the words we can make use of
B. “schoolroom” is used in the passage as an example of a specialized term
C. once you know how a word is pronounced and what it represents, you have turned it into your active word
D. active vocabulary refers to words we understand when we read and hear them
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