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.
单选题
【C1】
【正确答案】
A
【答案解析】解析：上句提到从月球上带回来的石块和泥土是放置在一个特制密封的铝盒里，能保持类似月球表面的低压环境(low-pressure environment)。从本句的But推断，这个密封装置可能出现了问题，下段提到月尘非常锋利(it cuts like glass)。因此A项destroyed“被破坏”符合语义逻辑，表明盒子被月尘破坏。
【答案解析】解析：本句说明月尘是如何形成的。从后面的伴随状语heating its rocks and dirt…to fineparticles(将石块和尘土加热并粉碎成颗粒)推断，流星对月球表面造成了极大冲击，导致这样的后果。B项crash意为“撞击”，符合语义逻辑。
单选题
【C4】
【正确答案】
C
【答案解析】解析：本句提到这些微小的颗粒既锋利又不平(sharp and uneven)，说明它们的边缘(edges)是不光滑的。C项rough有“粗糙”之意，语义符合。
单选题
【C5】
【正确答案】
D
【答案解析】解析：下一段提到月尘损坏了太空衣(damaged spacesuits)，并且提到月尘还附着在宇航员的身上被带回了太空船(Dust followed the astronauts back into their ships)，这说明月尘无处不在，具有很强的粘着力。D项cling to“附着”符合语义逻辑。