2. 外语
  3. Space is a dangerous place, not only because of meteors (流星) but also because of rays from the sun and other stars. The atmosphe

Space is a dangerous place, not only because of meteors (流星) but also because of rays from the sun and other stars. The atmosphe

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问题 Space is a dangerous place, not only because of meteors (流星) but also because of rays from the sun and other stars. The atmosphere again acts 【C1】______ our protective blanket on 【C2】______ . Light gets through, and this is essential 【C3】______ plants to make the food which we 【C4】______ . Heat, 【C5】______ , makes our environments tolerable and some ultraviolet rays (紫外线) penetrate the 【C6】______ . Cosmic (宇宙的) rays of various kinds come 【C7】______ the air from outer space, but 【C8】______ quantities of radiation from the sun are screened off. As 【C9】______ as men leave the atmosphere they are 【C10】______ to this radiation; 【C11】______ their spacesuits or the walls of their spacecraft, if they are inside, 【C12】______ prevent a lot of radiation damage.
    Radiation is the greatest known danger to explorers in 【C13】______ . Doses of radiation are measured in 【C14】______ called "rems (雷姆)". We all 【C15】______ radiation here on earth from the sun, from cosmic rays and from radioactive minerals. The" 【C16】______ "dose of radiation that we receive each year is about 100 millirems; it 【C17】______ according to where you live, and this is a very rough estimate. Scientists have reason to think 【C18】______ a man can 【C19】______ up with far more radiation
     【C20】______ this without being damaged; the figure of (60) rems has been agreed.
【C17】
选项 A、shifts
B、converts
C、modifies
D、varies
答案D
解析 词义辨析题，shift 意为“移动”，convery 意为“转换”，modify 意为“修改”，vary 意为“变化”，结合句意可知，所处地点不同，所受辐射量也不一样，所以D正确，考点 convert 和change 意思相同，但convert 通常指“从某种状态、某种用途、某种意向转变为另一种状态、用途和意向”，如水化为蒸汽、荒地变为良田、化喜为悲、改变信仰等，change 是最通俗的词，可以指各方面的改变，modify相当于make different，多用于指“修改计划、契约，改变方法、制度等”，如：The terms of the contract have been modified．该合同的条款已经修改过了，shift 强调转换，指“由一个人或结构到另一个的转变，或位置的变换、更替等”，如：The teacher shifted the chairs around in the classroom. 那位教师挪动了教室里的椅子
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大学英语四级

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