Space is a dangerous place, not only because of meteors(流星)but also because of rays from the sun and other stars.Theatmosphere again acts 1 _our protective blanket on 2_ .Lightgets through, and this is essential 3_ plants to make the foodwhich we 4_ .Heat, 5_ , makes our environments tolerable andsome ultraviolet rays(紫外线的) penetrate the 6_ .Cosmic(宇宙的) rays of various kinds come 7_ the air from outer space, but8_ quantities of radiation from the sun are screened off. 9 _menleave the atmosphere they are 10_ to this radiation; 11_ their spacesuits or the walls of theirspacecraft, if they are inside, 12_ prevent a lot of radiation damage.Radiation is the greatest knowndanger to explorers in 13 _.Doses of radiation are measured in 14 _called“rems (雷目)”.We all 15_radiation here on earth from the sun, from cosmic rays and from radioactive minerals.The“ 16_ ”dose of radiation that we receive each year is about two millirems; it 17_ according toswheresyoulive, and this is a very rough estimate.Scientists have reason to think 18_ a man can 19_ far moreradiation 20_ without being damaged; the figure of 60 rems has been agreed.
1.A.for B.with C.on D.as
2.A.stars B.sun C.earth D.space
3.A.with B.from C.under D.for
4.A.use B.live C.eat D.get
5.A.again B.also C.besides D.too
6.A.environment B.space C.atmosphere D.earth
7.A.across B.to C.from D.through
8.A.valid B.enormous C.various D.proper
9.A.As soon as B.As well as C.As much as D.As possible as
10.A.shown B.exposed C.faced D.covered
11.A.but B.because C.so D.so that
12.A.get B.make C.have D.do
13.A.earth B.atmosphere C.space D.environment
14.A.pieces B.units C.parts D.elements
15.A.receive B.accept C.bring D.catch
16.A.conventional B.commonC.general D.normal
17.A.shifts B.converts C.modifies D.varies
18.A.what B.which C.that D.why
19.A.put up with B.keep up with C.come up with D.catch up with
20.A.from B.than C.as D.away
1.【答案】D
【解析】act as“充当、起……作用”;act for“代表、代理”;act on“按照”。本句意为大气层起到保护伞的作用。
2.【答案】C
【解析】见上题分析。
3.【答案】D
【解析】be essential for“对……来说是首要的、基础的”，固定搭配。
4.【答案】C
【解析】只有eat与先行词food和定语从句which we…搭配。
5.【答案】D
【解析】本句意为：热不仅使我们的生产环境温度适宜，而且紫外线也能穿透大气。also一般紧跟动词;besides一般用在句前;too可用在句中，用逗号隔开。
6.【答案】C
【解析】根据上题所讲，penetrate这个动词后面应接atmosphere“大气”这个名词。
7.【答案】D
【解析】这里的come through相当于penetrate，穿透。come across“偶遇”;come to“来到”;come from“来自”。本句意为：各类来自外部空间的宇宙射线穿透大气层……，故选come through。
8.【答案】B
【解析】Valid有效的;various各种各样的;proper合适的。在四个选项中只有enormous表示“大量的”意思。
9.【答案】A
【解析】as soon as“只要”;as well as“除……之外”;as much as“和……一样多”;as possible as“尽可能的”。
10.【答案】B
【解析】be exposed to“暴露于”，show“展示”;face“面对”。
11.【答案】A
【解析】本句前半句的意思是：“人们一离开大气层就会接触射线”;后半句意思是：“他们的太空服和太空船会阻止射线造成的损害”。前后应该是转折关系，故用but。
12.【答案】D
【解析】Do +动词原型的结构表示强调谓语动词。
13.【答案】C
【解析】由radiation和explorers可推测，应选space(太空)。本句意为射线是探险者在太空遇见的已知的最大危险。
14.【答案】B
【解析】unit“单位、单元”;element“元素”;part“部分”;piece“碎片”本句意为：射线的多少可以以雷目这个测量单位测量。
15.【答案】A
【解析】receive表示客观收到;accept表示主观接受。我们受到的辐射并非主观接受。
16.【答案】D
【解析】conventional“传统的”;common“共同的、普通的”;general“一般的、总体的”;normal“正常的”。本句意为：我们每年接受的正常辐射量……，故选normal。
17.【答案】D中华考试网
【解析】shift“移动”;convert“转换”;modify“修改”;vary“变化”。根据句意，所处地点不同，所受辐射量也不一样……，故选varies.
编辑推荐：
更多信息请关注读书人网（http://www.reader8.net/）四六级频道！
