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Paragraph 4
A. Competing Explanations
B. Unknown Attacks
C. Mysterious Explosion
D. Star War
E. Importance of Finding Evidence
F. Explanation that Worries Scientists
B. Unknown Attacks
C. Mysterious Explosion
D. Star War
E. Importance of Finding Evidence
F. Explanation that Worries Scientists
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更多 “Paragraph 4A. Competing Explanations B. Unknown Attacks C. Mysterious Explosion D. Star War E. Importance of Finding Evidence F. Explanation that Worries Scientists” 相关考题
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What is the text mainly about?A. The research into war history.B. The finding of a forgotten hero.C. The pilots of the two world wars.D.The importance of military studies.
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The word “thaw”(Line 3, Paragraph 4) most probably means _____ .［A］ aggravation of tension［B］ improvement in relation［C］ intensification in attacks［D］ ending of coordination
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The most ______evidence of black holes comes from research into binary star systems.A. convincingB. convinceC. convincedD. convinces
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The most______(convince)evidence of black holes comes from research into binary star systems.
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Finding a solution to this problem is one of the greatest ________ faced by scientists today.
A. difficultiesB. difficultyC. difficultD. difficiency
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Which two of these multicast deployments are most susceptible to attacks from unknown sources?()
A.ASMB.BiDirPIMC.PIM-SMRPD.RP-SwitchoverE.SourceSpecificMulticast
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The purpose of non-REM sleep is even more mysterious. The new experiments, such as those _____ for the first time at a recent meeting or the society for Sleep Research in Minneapolis, suggest fascinating explanations for the purpose of non-REM sleep.[A] maintained[B] described[C] settled[D] afforded
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To the scientists' delight, their efforts have increased people's _______of the importance of saving water.
A．awareness
B．commitment
C．agreement
D．response
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The purpose of non‐REM sleep is even more mysterious.The new experiments,such as those（ ）for the first time at a recent meeting or the society for Sleep Research in Minneapolis,suggest fascinating explanations for the purpose of non REM sleep.A.maintained
B.described
C.settled
D.afforded
考题
资料：It’s easy to trace the evolution of the automobile.At most，we’re only talking about a few centuries of technological development，and most of the plans，prototypes and models are still around. With just a little research，you can easily trace the latest model electric hybrid back to its steam-powered ancestors.
Your family tree is probably a different matter. Even an extensive genealogy chart can only reach back so far，and mortality puts a rather strict limit on exactly how many “models” are still on the road. Humanity’s evolutionary progression is even more difficult. We still have plenty of living primate relatives，but many of the life forms that connect the evolutionary dots are long extinct.
Evolutionary biologists use several methods to decipher exactly how we came to be as we are.In fact，the field itself encompasses several different disciplines in addition to biology，like genetics，psychology，geology，archaeology linguistics，anthropology and primatology just to name a few. Naturally，paleoanthropology also plays a key role，as we have to turn to the fossil record for many clues about our ancient primate，human and nearly human ancestors.
While the fossil record by its very nature is incomplete，there’s no shortage of fossil evidence to link the planet’s varied life forms into a great tree of life， a chart that scientists call a phylogenetic tree. You can think of humans as the very tip of just one branch on that tree called “hominid.” Chimpanzees exist at the end of an adjoining branch called “panin.” Follow both the hominid and panin branch back about 5.4 million years， and you’ll find a point where scientists think the two converged from a single，common ancestor.
Fossil evidence helps scientists to reconstruct these trees，but so do morphological and genetic studlies. Genetic analysis has yielded striking similarities between chimps and humans. As such， scientists know a last common ancestor of chimps and humans existed，even if we’ve yet to determine the exact species. Yet paleoanthropologists have found numerous hominid fossils to bridge the evolutionary progression from that unknown common ancestor to modern humans. These finds include such famous East African fossils as Lucy（Australopithecus afarensis），which strengthened the importance of bipedalism in human evolution and proved an essential milestone on our way to modern Homo sapiens.
Fossil evidence for human evolution will never be complete，as fossils themselves are rare geologic occurrences.Nevertheless，by incorporating other scientific disciplines，we’re able to build an increasingly accurate picture of just what our evolutionary family tree consisted of.
What can be inferred from Para.5?A.Morpholoical and genetic studies helped scientists to trace unknown common ancestor of chimps and humans existed.
B.Morphological and genetic studies determined exact species of common ancestor of chimps and humans existed.
C.Genetic studies found hominid fossils to bridge the evolutionary progression from unknown common ancestor to modern humans.
D.Morphological studies helped finding the famous East African fossils and set up an milestone in this field.
考题
Paragraph 3A. Competing Explanations
B. Unknown Attacks
C. Mysterious Explosion
D. Star War
E. Importance of Finding Evidence
F. Explanation that Worries Scientists
考题
Black Holes Trigger Stars to Self-Destruct
Scientists have long understood that supermassive black holes weighing millions or billions of suns can tear apart stars that come too close. The black hotels gravity pulls harder on the nearest part of the star, an imbalance that pulls the star apart over a period of minutes or hours, once it gets close enough.
Scientists say this Uneven pulling is not the only hazard facing the star. The strain of these unbalanced forces can also trigger a nuclear explosion powerful enough to destroy the star from within. Matthieu Brassart and Jean-Pierre Luminet of the Observatoire de Paris in Meudon, France, carried out computer simulations of the final moments of such an unfortunate star's life,as it veered towards a supermassive black hole.
When the star gets close enough, the uneven forces flatten it into a pancake shape. Some previous studies had suggested this flattening would increase the density and temperature inside the star enough to trigger intense nuclear reactions that would tear it apart. But other studies had suggested that the picture would be complicated by shock waves generated during the flattening process and that no nuclear explosion should occur.
The new simulations investigated the effects of shock waves in detail,and found that even when their effects are included,the conditions favor a nuclear explosion. "There will be an explosion of the star-it will be completely destroyed," Brassart says. Although the explosion obliterates the star, it saves some of the star's matter from being devoured by the black hole. The explosion is powerful enough to hurl much of the star's matter out of the black hole's reach, he says.
The devouring of stars by black holes may already have been observed, although at a much later stage. It is thought that several months after the event that rips the star apart,its matter starts swirling into the hole itself. It heats up as it does so, releasing ultraviolet light and X-rays.
If stars disrupted near black holes really do explode, then they could in principle allow these events to be detected at a much earlier stage, says Jules Hatpern of Columbia University in New York, US. "It may make it possible to see the disruption of that star immediately if it gets hot enough," he says.
Brassart agrees. "Perhaps it can be observed in the X-rays and gamma rays, but it's something that needs to be more studied," he says. Supernova researcher Chris Fryer of the Los Alamos National Laboratory in Los Alamos, New Mexico, US, says the deaths of these stars are difficult to simulate, and he is not sure whether the researchers have proven their case that they explode in the process.
文章(36~40)
Something destructive could happen to a star that gets too close to a black hole. Which of the following destructive statements is NOT mentioned in the passage?A. The black hole could tear apart the star.
B. The black hole could trigger a nuclear explosion in the star.
C. The black hole could dwindle its size considerably.
D. The black hole could devour the star.
考题
According to the fourth paragraph, which of the following is NOT true?A. No nuclear explosion would be triggered inside the star.
B. The star would be destroyed completely.
C. Much of the star's matter thrown by the explosion would be beyond the black hole's reach.
D. The black hole would completely devour the star.
考题
What will happen several months after the explosion of the star?A. The star's matter will move further away from by the black hole.
B. The black hole’s matter will heat up.
C. The torn star's matter will swirl into the black hole.
D. The black hole's matter will release ultraviolet light and X-rays.
考题
Tunguska Event
1 A hundred years ago this week, a gigantic explosion ripped (撕裂) open the day y above a forest in western Siberia, leaving a scientific riddle that endures to this day.
2 A dazzling light pierced the heavens, followed by a shock wave as strong as 1,000 atomic bombs. The explosion flattened 80 million trees across an area of 2,000 square kilometers. The fireball was so great that, a day later, Londoners could read their newspapers under the night sky. What caused the so-called Tunguska Event, named after the nearby Podkamennaya Tunguska River, still remains a mystery.
3 Experts suspect it was a rock that, after traveling in space for millions of years, was destined to crash to Earth at exactly 7:17 a.m. on June 30, 1908. This possibility worries scientists. “Imagine an unspotted asteroid (小行星) hitting a significant chunk(块) of land ... and imagine if that area, unlike Tunguska, were populated,” the British science journal Nature commented recently.
4 But no fragments of the “rock” have ever been found. Finding such evidence would be important, for it would increase our knowledge about the risk posed by dangerous Near Earth Objects (NEOs), say Italian researchers Luca Gasperini, Enrico Bonatti and Giuseppe Longo. When the next Tunguska NEO approaches, scientists will have to decide whether to try to deflect (使偏转) it or blow it up in space.
5 However, several rival theories for the Tunguska Event exist. Wolfgang Kundt, a professor at Germany's Bonn University, believes the Tunguska Event was caused by a massive escape of 10 million tons of methane(甲烷)-rich gas from deep within earth's crust. Some people hold that the explosion was caused by an alien spaceship crash, or a black hole in the universe.
文章(23~30)
Paragraph 2A. Competing Explanations
B. Unknown Attacks
C. Mysterious Explosion
D. Star War
E. Importance of Finding Evidence
F. Explanation that Worries Scientists
考题
Which of the following best describes the organization of the last paragraph of the passage？( ) A.An observation is made and qualifications of it are provided.
B.A phenomenon is noted and explanations for it are presented.
C.A hypothesis is presented and arguments against it are cited.
D.A prognosis is made and evidence supporting it is discussed.
考题
Which two of these multicast deployments are most susceptible to attacks from unknown sources?（）A、ASMB、BiDirPIMC、PIM-SMRPD、RP-SwitchoverE、SourceSpecificMulticast
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Which two of these multicast deployments are most susceptible to attacks from unknown sources？（）A、 ASMB、 BiDir PIMC、 PIM-SM RPD、 RP-SwitchoverE、 Source Specific Multicast
考题
Which Cisco security software product mitigates Day Zero attacks on desktops and servers - stopping known and unknown attacks without requiring reconfigurations or updates on the endpoints？（）A、 Cisco Secure Desktop （CSD）B、 NAC Appliance Agent （NAA）C、 Cisco SecurityAgent （CSA）D、 SSLVPN Client （SVC）E、 Cisco TrustAgent （CTA）
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多选题Which two of these multicast deployments are most susceptible to attacks from unknown sources?（）AASMBBiDirPIMCPIM-SMRPDRP-SwitchoverESourceSpecificMulticast
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单选题No one reason given for the fall of Rome are adequate explanations on their own, but many reasons taken together provide a clear picture as to why the once mighty empire did not last.A
are adequate explanations all on theirB
are an adequate explanation on itsC
adequately explain on theirD
offers an adequate explanation on theirE
is an adequate explanation on its
考题
单选题In the second paragraph, the author shows ______.A
the researchers' findingsB
the importance of familyC
the importance of moneyD
the importance of career
考题
单选题Which Cisco security software product mitigates Day Zero attacks on desktops and servers - stopping known and unknown attacks without requiring reconfigurations or updates on the endpoints？（）A
Cisco Secure Desktop （CSD）B
NAC Appliance Agent （NAA）C
Cisco SecurityAgent （CSA）D
SSLVPN Client （SVC）E
Cisco TrustAgent （CTA）
考题
多选题Which two of these multicast deployments are most susceptible to attacks from unknown sources？（）AASMBBiDir PIMCPIM-SM RPDRP-SwitchoverESource Specific Multicast
考题
单选题Paragraph 1 mainly talks about _____.A
the reasons for successB
the meaning of successC
the standards of successD
the importance of success
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