22.【题干】The US income tax system will be simplified in the next few years.
A.Right
B.Wrong
C.Not mentioned
概括大意与完成句子
Tunguska Event
1 A hundred years ago this week, a giganticexplosion ripped (撕裂) open the day y above a forest in western Siberia, leaving ascientific 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 explosionflattened 80 million trees across an area of 2,000 square kilometers. Thefireball was so great that, a day later, Londoners could read their newspapersunder the night sky. What caused the so-called Tunguska Event, named after thenearby Podkamennaya Tunguska river, still remains a mystery.
3 Experts suspect it was a rock that, aftertraveling in space for millions of years, was destined to crash to Earth atexactly 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, werepopulated,” the British science journal Nature commented recently.
4 But no fragments of the “rock” have everbeen found. Finding such evidence would be important, for it would increase ourknowledge about the risk posed by dangerous Near Earth Objects (NEOs), sayItalian researchers Luca Gasperini, Enrico Bonatti and Giuseppe Longo. When thenext Tunguska NEO approaches, scientists will have to decide whether to try todeflect (使偏转) it or blowit up in space.
5 However, several rival theories for theTunguska Event exist. Wolfgang Kundt, a professor at Germany's Bonn University,believes the Tunguska Event was caused by a massive escape of 10 million tonsof methane(甲烷)-rich gasfrom deep within earth's crust. Some people hold that the explosion was causedby an alien spaceship crash, or a black hole in the universe.
23. Paragraph 2
24. Paragraph 3
25. Paragraph 4
26. Paragraph 5
A. Competing Explanations
B. Unknown Attacks
C. Mysterious Explosion
D. Star War
E. Importance of Finding Evidence
F. Explanation that Worries Scientists
27. The giganticexplosion that occurred a hundred years ago
28. The shock wavewhich followed the dazzling light
29. The hypothesisthat the explosion was caused by a rock colliding with the Earth
30. Wolfgang Kundt,who has developed an alternative theory
A. has remained a puzzle
B. lacks sufficient evidence
C. is a university professor
D. was generated by the explosion
E. will kill many animals
F. are attacked by aliens
阅读理解
Don’t count on dung
Conservationists (自然保护主义者) may be miscalculating the numbers of the threatened animals such as elephants, say African and American researchers. The error occurs because of a flaw in the way they estimate animal numbers from the piles of dung (粪) the creatures leave behind.
The mistake could lead researchers to think that there are twice as many elephants as there really are in some regions, according to Andrew Plumptre of the Wildlife Conservation Society (WCS) in New York.
Biologist Katy Payne of Cornell University in Ithaca, New York, agrees. "We really need to know elephant numbers and the evidence that we have is quite indirect," says Payne, who electronically tracks elephants.
Counting elephants from planes is impossible in the vast rainforests of Central Africa. So researchers often estimate elephant numbers by counting dung piles in a given area. They also need to know the rate at which dung decays: Because it's extremely difficult to determine these rates, however, researchers counting elephants in one region tend to rely on standard decay rates established elsewhere.
But researchers at the WCS have found that this decay rate varies from region to region depending on the climate and environment. Using the wrong values can lead the census astray (离开正道), says Plumptre.
He and his colleague Anthony Chifu Nchanji studied decaying elephant dung in the forests of Cameroon. They found that the dung decayed between 55 and 65 per cent
more slowly than the dung in the rainforests of neighbouring Gabon. If researchers use decay rates from Gabon to count elephants in Cameroon, they would probably find more elephants than are actually around.
This could mean estimates in Cameroon are at least twice as high as those derived from decay rates calculated locally, says Plumptre. "However accurate your dung density estimate might be, the decay rate can severely affect the result."
Plumptre also says that the dung-pile census should be carried out over a region similar in size to an elephant's natural range. The usual technique of monitoring only small, protected areas distorts numbers because elephants move in and out of these regions, he says. "If the elephant population increases within the protected area, you can not determine whether it is a real increase or whether it is due to elephants moving in because they are being poached (入侵偷猎) outside."
Plumptre says that similar problems may also affect other animal census studies that rely on indirect evidence such as nests, tracks or burrows (地洞).
1 The word "threatened" in the first sentence of the first paragraph could be best replaced by
A "endangered".
B "frightened".
C "killed".
D "angered".
2 Why do researchers estimate elephant numbers in an area by counting dung piles?
A Because elephants are difficult to catch.
B Because it is not possible to count elephants from a plane.
C Because it is not possible to keep track of elephants.
D Because elephants are shy animals.
3 Piles of dung can't be relied upon when it comes to estimating elephant numbers because
A they are different in size.
B they scatter all over the region.
C they are different in decay rate.
D they are different in quality.
4 According to Plumptre, the region over which a dung-pile census is carried out should be
A small enough.
B well protected.
C carefully monitored.
D large enough.
5 The first word "He" in paragraph 6 refers to
A Andrew Plumptre.
B Katy Payne.
C Anthony Chifu Nchanji.
D the writer of the article.
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.
36.【题干】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.
37.【题干】According to the third paragraph, researchers differed from each other in the problem of_____
A. whether nuclear reaction would occur.
B. whether the stars would increase its density and temperature.
C. whether shock waves would occur.
D. whether the uneven forces would flatten the stars.
38.【题干】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.
39.【题干】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.
40.【题干】According to the context, the word "disruption" in Paragraph 6 means_____
A. "Confusion."
B. "Tearing apart."
C. "Interruption."
D. "Flattening."
