历年六级阅读真题练习[3]_CET真题
passage two
questions 26 to 30 are based on the following passage:
there are some each phenomena you can count on, but the magnetic field, someday is not of them. it fluctuates in strength, drifts from its axis, and every few 100,000 years undergo, dramatic polarity reversal-a period when north pole becomes south pole and south pole become north pole. but how is the field generated, and why is it so unstable?
groundbreaking research by two french geophysicists promises to shed some light on the mystery. using 80 meters of deep sea sediment（沉淀物）core, they have obtained measure, lots of magnetic-field intensity that span 11 polarity reversals and four million years. the analysis reveals that intensity appears to fluctuate with a clear, well-defined rhythm. although the strength of the magnetic field varies irregularly during the short term, there seems to be an inevitable long-term decline preceding each polarity reversal. when the poles flip-a process that takes several hundred thousand years-the magnetic field rapidly regains its strength and the cycle is repeated.
the results have caused a stir among geophysicists. the magnetic field is thought to originate from molten（熔化的）iron in the outer core, 3,000 kilometers beneath the earth's surface. by studying mineral grains found in material ranging from rocks to clay articles, previous researchers have already been able to identify reversals dating back 170 million years, including the most recent switch 730,000 years ago. how and why they occur, however, has been widely debated. several theories link polarity flips to external disasters such as meteor（陨星）impacts. but peter olson, a geophysicist at the johns hopkins university in baltimore, says this is unlikely if the french researchers are right. in fact, olson says intensity that predictably declines from one reversal to the next contradicts 90 percent of the models currently under study. if the results prove to be valid geophysicists will have a new theory to guide them in their quest to understand the earth's inner physics. it certainly points the direction for future research.
26. which of the following titles is most appropriate to the passage?
a) polarity reversal: a fantastic phenomenon of nature
b) measurement of the earth's magnetic-field intensity
c) formation of the two poles of the earth
d) a new approach to the study or geophysics
27. the word "flip" (line 6, para.2) most probably means "__________".
a) decline
b) intensify
c) fluctuate
d) reverse
28. what have the two french geophysicists discovered in their research?
a) some regularity in the changes of the earth's magnetic field.
b) some causes of the fluctuation of the earth's magnetic field.
c) the origin of the earth's magnetic field.
d) the frequency of polarity reversals.
29. the french geophysicists' study is different from currently prevailing theories in ________.
a) its identification of the origin of the earth's magnetic field
b) the way the earth's magnetic intensity is measured
c) its explanation of the shift in the earth's polarity
d) the way the earth's fluctuation rhythm is defined
30. in peter olson's opinion the french experiment ______.
a) is likely to direct further research in the inner physics of the earth
b) has successfully solved the mystery of polarity reversals
c) is certain to help predict external disasters
d) has caused great confusion among the world's geophysicists
译文
有些地球现象可以预计，但有的人说磁场是个例外。磁场的强度波动，并从轴开始移动，每隔几十万年经历一次奇异的两极转换--这期间北极变成南极，南极变成北极。但磁场是怎么产生的？为什么如此不稳定？
passage two
questions 26 to 30 are based on the following passage:
there are some each phenomena you can count on, but the magnetic field, someday is not of them. it fluctuates in strength, drifts from its axis, and every few 100,000 years undergo, dramatic polarity reversal-a period when north pole becomes south pole and south pole become north pole. but how is the field generated, and why is it so unstable?
groundbreaking research by two french geophysicists promises to shed some light on the mystery. using 80 meters of deep sea sediment（沉淀物）core, they have obtained measure, lots of magnetic-field intensity that span 11 polarity reversals and four million years. the analysis reveals that intensity appears to fluctuate with a clear, well-defined rhythm. although the strength of the magnetic field varies irregularly during the short term, there seems to be an inevitable long-term decline preceding each polarity reversal. when the poles flip-a process that takes several hundred thousand years-the magnetic field rapidly regains its strength and the cycle is repeated.
the results have caused a stir among geophysicists. the magnetic field is thought to originate from molten（熔化的）iron in the outer core, 3,000 kilometers beneath the earth's surface. by studying mineral
grains found in material ranging from rocks to clay articles, previous researchers have already been able to identify reversals dating back 170 million years, including the most recent switch 730,000 years ago. how and why they occur, however, has been widely debated. several theories link polarity flips to external disasters such as meteor（陨星）impacts. but peter olson, a geophysicist at the johns hopkins university in baltimore, says this is unlikely if the french researchers are right. in fact, olson says intensity that predictably declines from one reversal to the next contradicts 90 percent of the models currently under study. if the results prove to be valid geophysicists will have a new theory to guide them in their quest to understand the earth's inner physics. it certainly points the direction for future research.
26. which of the following titles is most appropriate to the passage?
a) polarity reversal: a fantastic phenomenon of nature
b) measurement of the earth's magnetic-field intensity
c) formation of the two poles of the earth
d) a new approach to the study or geophysics
27. the word "flip" (line 6, para.2) most probably means "__________".
a) decline
b) intensify
c) fluctuate
d) reverse
28. what have the two french geophysicists discovered in their research?
a) some regularity in the changes of the earth's magnetic field.
b) some causes of the fluctuation of the earth's magnetic field.
c) the origin of the earth's magnetic field.
d) the frequency of polarity reversals.
29. the french geophysicists' study is different from currently prevailing theories in ________.
a) its identification of the origin of the earth's magnetic field
b) the way the earth's magnetic intensity is measured
c) its explanation of the shift in the earth's polarity
d) the way the earth's fluctuation rhythm is defined
30. in peter olson's opinion the french experiment ______.
a) is likely to direct further research in the inner physics of the earth
b) has successfully solved the mystery of polarity reversals
c) is certain to help predict external disasters
d) has caused great confusion among the world's geophysicists
译文
有些地球现象可以预计，但有的人说磁场是个例外。磁场的强度波动，并从轴开始移动，每隔几十万年经历一次奇异的两极转换--这期间北极变成南极，南极变成北极。但磁场是怎么产生的？为什么如此不稳定？
两位法国地球学家的开创性研究为揭示这一奥秘提供了一些线索。利用80米深海沉淀物的核心，他们测出了历时400万年，11次两极转换期间的磁场强度。分析显示，强度的波动看来有明显、准确的节奏。虽然短期内磁场强度变化不规则，但似乎每次两极转换前都有一个不可避免的漫长衰落过程。当两极转换后--一个历时几十万年的过程，磁场迅速恢复其强度，循环便重新开始。
这些结果引起了地球学家们的震惊。人们认为磁场源于地表下3000公里处地核外层熔化的铁。通过研究各种岩石和粘土等物质中发现的矿物颗粒，以前的研究者已经能够识别上溯一亿七千万年以来的两极转换，包括最近73万年前的那次转换。然而，这种转换是如何发生的？为什么会发生？家们争论激烈。有几种理论把两极转换同陨星碰撞这种外来灾难联系起来。但是，在巴尔的摩的约翰斯-霍布金斯大学的地球物理学家彼得·奥尔森说，如果法国研究者正确的话，这几种理论就不可能成立了。奥尔森说，实际上两次转换间预计的衰落强度同90%的现行研究模式相矛盾。如果这些结果证明正确，地球物理学家将会有一种新理论来指导他们探索地球内部学。它的确为将来的研究指出了方向。
正确答案：26. a 27. d 28. a 29. c 30. d