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 atmosphere

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

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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。
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