30. What is the writer’s attitude towards the hot-spot approach?

　　A) Critical. B) Neutral. C) Supportive. D) Doubtful.

　　Part IV Cloze (15 minutes)

　　Directions: There are 20 blanks in the following passage. For each blank there are four choices marked A), B), C) and D). You should choose the ONE that best fits into the passage.

　　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 (沖擊) 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. All sorts of mutational (突變) 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 the second 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 only occurred 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