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 theevent 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 inprinciple allow these events to be detected at a much earlier stage, says JulesHatpern of Columbia University in New York, US. "It may make it possible to seethe 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 researcherChris 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 surewhether the researchers have proven their case that they explode in theprocess.

31.题干】Something destructive could happen to a star that gets too close to ablack hole. Which of the following destructive statements is NOT mentioned inthe passage?

选项】

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.

答案】C

解析】

32.题干】According to the third paragraph，researchers differed from each otherin the problem of_____

选项】

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.

答案】A

解析】

33.题干】According to the fourth paragraph，which of the following is NOTtrue?

选项】

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 blackhole's reach.

D.The black hole would completely devour the star.

答案】D

解析】

34.题干】What will happen several months after the explosion of the star?

选项】

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.

答案】C

解析】

35.题干】According to the context，the word "disruption" in Paragraph 6means_____

选项】

A."Confusion."

B."Tearing apart."

C."Interruption."

D."Flattening."

答案】B

解析】

第二篇 Deforestation and Desertification(沙漠化)

TheSahel zone lies between the Saharadesert and the fertilesavannahs(热带大草原)ofnorthern Nigeria and South Sudan. The word sahel comes fromArabic and means marginal or transitional ,andthis is a good description ofthesesemi-arid(半干旱)lands,whichoccupy much of the Western African countries ofMail,Mauritania,Niger,and Chad.

Unfortunately, over the last century theSahara desert has steadily creptsouthwards eating into once productive Sahellands. United Nations surveys showthat over 70 percent of the dry land inagriculture use in Africa hasdeterioratedover the last 30 years. Droughts have become more severe, the mostrecentlasting over twenty years in parts of the Sahel region. The same processofdesertification is taking place across southern Africa as the Kalaharidesertadvances into Botswana and parts of South Africa.

One ofthe major causes of this desert advance ispoor agricultural land use,driven by the pressures of increasing population.Overgrazing一 keeping too manyfarm animals on the land一means that grasses and other plants cannot recover, andscarce water suppliesare exhausted. Overcultivation一 tryingto grow too manycrops on poor land一 resultsin the soil becoming even less fertile and drier, andbeginning to break up. Soilerosion (侵蚀) follows, and the land turns intodesert.

Another cause of desertification is loss of tree cover. Trees are cutdown foruse as fuel and to clear land for agricultural use. Tree roots help tobind thesoil together, to conserve moisture, and to provide a habitat forother plantsand animals. When trees are cut down, the soil begins to dry andloosen, wind andrain erosion increase, other plant species die, and eventuallythe fertile topsoil may be almost entirely lost, leaving only bare rock anddust.

The effects of loss of topsoil and increased drought are irreversible.Theyare,however, preventable. Careful conservation of tree cover andsustainableagricultural land use have been shown to halt deterioration of soilsand lessenthe effects of shortage of rainfall. One project in Kita in south-westMalifunded by UNDP has involved local communities in sustainable managementofforest,while at the same time providing a viable(有活力的)agriculturaleconomy.This may be a model for similar projects in otherWest African countries.

35 order to prevent desertification,the author proposes ___.

A. making good use of international aids

B. developing a sustainableagricultural economy

C. gaining international support

D. converting agricultural land intoforest

答案：b

36.The Sahel zone is an area which ___.

A. is covered with sad and grass

B. has a long history

C. occupies much of South Nigeria

D. belongs to Sudan

答案：a

37. What is the situation about thedesertification in Africa?

A. The deserts are replaced withgrasslands

B. The deserts are expanding

C. the deserts are moving northwards

D. the deserts are being deserted

答案：b

38. The word “deteriorated ” in paragraph2 means ___.

A. deepened

B. suffered

C. slipped

D. worsened

答案：d

39. What is the root cause