Two million years ago, just as the Earth’s primitive apemen were evolving into big-brained humans, a pair of supernovae explosions occurred near Earth. Our planet was buffeted (冲击) with blasts of radiation — with 31 effects. “These supernovae would 32 away our protective ozone layer,” said Dr Narciso Benitez of Johns Hopkins University. Earth lost its protection 33 ultraviolet light.

　　mutational (突变) damage to animals’ DNA would have occurred. New species could have emerged 34 . It is possible that Homo sapiens (智人) may have been one of these. The likely 35 of a supernova’s radiation led scientists in the past 36 that one may have affected 37 on Earth. Benitez now believes that 38 two supernovae occurred near Earth two million years ago: The first would have blasted space free 39 interstellar particles; and

　　would have struck Earth at full force, 40 its ozone layer.

　　Observations of space around our Sun have revealed that, 41 the rest of the galaxy, space near us has little interstellar gas in it. “ 42 it is missing much of its dust and gas — just as if a supernova 43 it out,” added Maíz-Apellániz. 44 , our tiny corner of the galaxy appears to have been swept clean by a supernova brush about two million years ago; and intriguingly, at just this time, a set of extinctions — known as the Pliocene (上新世) / Pleistocene (更新世) extinctions — is also known 45 .

　　It was also around this time that mankind’s direct ancestor, Homo erectus, the species 46 to be the first true human being, appeared in Africa and Asia after 47 more primitive ape-like creatures. These beings may have been some of the lucky few who were able to 48 advantage of conditions in these hazardous, radioactive 49 . This triumph

　　thanks to this celestial (上天的) 50 , however.

　　31. A) devastate B) devastating C) devastated D) devastation

　　32. A) blow B) have blown C) blew D) be blowing

　　33. A) in B) on C) against D) to

　　34. A) as a result of B) as a result C) the end result D) from the result of

　　35. A) compact B) contact C) intact D) impact

　　36. A) speculate B) speculating C) to speculate D) speculated

　　37. A) evolution B) revolution C) resolution D) solution

　　38. A) at least B) at most C) at first D) at last

　　39. A) with B) without C) at D) of

　　40. A) destroyed B) to destroy C) destroying D) destroy

　　41. A) unlikely B) likely C) unlike D) dislike

　　42. A) Definitely B) Obviously C) Eventually D) Essentially

　　43. A) would clean B) cleaned C) have cleaned D) had cleaned

　　44. A) In word B) In words C) In other words D) In a word

　　45. A) to occur B) to have occurred C) occurring D) have occurred

　　46. A) considered B) was considered C) considering D) being considered

　　47. A) placing B) replacing C) being placed D) being replaced

　　48. A) get B) gain C) win D) take

　　49. A) reasons B) results C) spaces D) times

　　50. A) invention B) intervention C) convention D) creation

　　答案解析:

　　Part IV Cloze

　　31. B)。该空应该填入一个形容词。A)为动词，C)为动词的过去分词，意为“被破坏的”，D)为名词，B)为动词的现在分词，可用作形容词，意为“破坏性的”。故B)为正确选项。

　　32. B)。此处表示对过去事情的推测，形式应该是would have done，blow的过去分词形式为blown，故应填入have blown。

　　33. C)。protection/protect在表示“保护某物免受……损害”时常与against或from连用，该空所在的句子表达“保护地球免受紫外线辐射的损害”，故介词选用C)。

　　34. B)。此题考查与result相关的短语，因为该空后没有宾语，所以先排除A)as a result of(作为结果)和D)。B)的意思是“结果”;C)意为“最终结果”，名词性短语。将B)代入待填空，整句的意思是“结果可能出现了新的物种”。

　　35. D)。此题考查形近词的辨析。四个选项的意思分别是：紧凑的;联系;完整无缺的;影响。该空要填入名词，先将C)排除。将其他三词带入原文，符合句意要求的是impact，填入该词后，该部分的意思是：超新星辐射的可能影响。

　　36. C)。lead的搭配是lead sb. to do，意思是“使得某人做某事”。

　　37. A)。此题考查形近词的辨析。四个选项的意思分别是：进化;革命;决心;解决办法。根据文章的主题句即第一段的第一句可推知，超新星辐射可能会对地球上的生物进化产生影响。

　　38. A)。根据句意推断，此处说的是“在地球周围至少产生了两颗超新星”。

　　39. D)。 此题考查介词搭配。free of ...表示“没有……的”。

　　40. C)。该题考查非谓语形式作状语，由于destroy的动作执行者是主句的主语，所以应该用destroy的现在分词形式，在该词后直接加ing。

　　41. C)。待填空应该填入介词，A)和B)是形容词或副词，D)为名词或动词，只有C)unlike(和……不同)为介词。

　　42. D)。根据句意可知，此处讲的是地球周围的太空中星际气体含量很少，实质上大部分星际气体和尘埃都消失了。

　　43. D)。as if表示“好像”，其引导的方式状语从句要用虚拟语气，表示对过去事情的虚拟，要用had done形式。

　　44. C)。本题考查与word有关的短语搭配，一般不用短语in word和in words，先将A)和B)排除;C) in other words意为“换言之”;D)in a word意为“一句话，总而言之”。该空后面的内容是对前文的解释说明，而不是总结。

　　45. B)。表示“被……所了解”用be known to sb.，由于occur的动作发生在know之前，故选用完成式。

　　46. A)。由于该句的主句已经存在，所以该空所在的部分应该处理成非谓语形式，又因为species和consider构成被动关系，所以应该用过去分词形式。

　　47. B)。place意为“放置”，replace意为“代替”，原文要表达的是“取代了”而不是“被取代”类猿生物。

　　48. D)。原文想要表达的是“这些生物可能是为数不多的利用了当时条件的幸运儿”，短语take advantage of的意思正是“利用”，为答案。

　　49. D)。此处意为“在那冒险的、产生放射性物质的时期”。times在此处意为“时期”。

　　50. B)。发生在地球附近的两颗超新星发生的爆炸，可以看作是上天的intervention(干预)，而不是invention(发明)、convention(惯例)和creation(创造)。