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.
【C3】
选项 A、with
B、from
C、under
D、for
答案D
解析 惯用搭配题，be essential for 意为“对…来说是首要的，基础的”，是惯用搭配，所以D正确，考点 essential 意为“必需的，基本的，本质的”，词义比necessary 更强，也更郑重，就事物的本质而言，含义比较绝对，如：It is essential for us to try to decide whether television is a blessing or a curse．我们有必要来评判电视到底是福还是祸
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大学英语四级

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