When Neil Armstrong and Buzz Aldrin returned from the moon, their cargo included nearly fifty pounds of rock and soil, which wer

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问题     When Neil Armstrong and Buzz Aldrin returned from the moon, their cargo included nearly fifty pounds of rock and soil, which were packed in an aluminum box with seals designed to maintain the lunar surface’s low-pressure environment. But back at Johnson Space Center, in Houston, scientists discovered that the seals had been【C1】________—by moon dust.
    Lunar dust is fine, like a powder,【C2】________it cuts like glass. It’s formed when shooting stars【C3】________on the moon’s surface, heating its rocks and dirt and reducing them to fine particles. Since there’s no wind or water to smooth【C4】________edges, the tiny grains are sharp and uneven, and【C5】________nearly everything.
    "The intruding【C6】________of lunar dust represents a more challenging engineering design issue, as well as a【C7】________issue for settlers, than does radiation," wrote Harrison Schmitt, an Apollo 17 astronaut, in his 2006 book, "Return to the Moon." The dust damaged space-suits and ate away layers of moon boots. Over the【C8】________ of six Apollo missions, not one rock box【C9】________its vacuum seal. Dust followed the astronauts back into their ships, too. According to Schmitt, it smelled like gunpowder and made breathing【C10】________. No one knows precisely what the extremely small particles do to human lungs.
    The dust not only【C11】________the moon’s surface, but floats up to sixty miles【C12】________it—as an outer part of its atmosphere, where particles【C13】________the moon by gravity, but are so thin that they【C14】________collide. In the nineteen-sixties, Surveyor probes filmed a glowing cloud floating just above the lunar surface during sunrise. Later, Apollo 17 astronaut Gene Cernan, while orbiting the moon, recorded a【C15】________phenomenon at the sharp line where lunar day meets night. Cernan【C16】________a series of pictures illustrating the changing【C17】________; streams of particles popped【C18】________the ground and hovered, and the resulting cloud came into sharper focus as the astronauts’ orbiter approached daylight. Since there’s no wind to form and【C19】________the clouds, their origin is something of a mystery. It’s【C20】________that they’re made of dust, but no one fully understands how or why they do their thing.
【C10】

选项 A、even
B、fast
C、difficult
D、comfortable

答案C

解析 本句提到月尘闻起来像火药(it smelled like gunpowder),火药的味道一般是很浓并让人呼吸不畅。C项difficult “困难的”,代入后指呼吸困难。A项even、B项fast和D项comfortable分别表示“均匀的”、“快速的”和“舒服的”,闻起来像火药的月尘不会使人呼吸均匀或舒服,也不会使呼吸加快。
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