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  3. The Moon, which has undergone a distinct and complex geological history, presents a striking appearance. The moon may be divided

The Moon, which has undergone a distinct and complex geological history, presents a striking appearance. The moon may be divided

admin2010-03-19  61
问题      The Moon, which has undergone a distinct and complex geological history, presents a striking appearance. The moon may be divided into two major terrains: the maria (dark lowlands) and the terrace (bright highlands). The contrast in the reflectivity (the capability of reflecting light) of these two terrains suggested to many early observers that the two terrains might have different compositions, and this supposition was con firmed by missions to the Moon such as Surveyor and Apollo. One of the most obvious differences between the terrains is the smoothness of the maria in contrast to the roughness of the highlands. This roughness is mostly caused by the abundance of craters; the highlands are completely covered by large craters (greater than 4050km in diameter), while the craters of the maria tend to be much smaller. It is now known that the vast majority of the Moon’s craters were formed by the impact of solid bodies with the lunar surface.
     Most of the near side of the Moon was thoroughly mapped and studied from telescopic pictures years before the age of space exploration. Earth-based telescopes can resolve objects as small as a few hundred meters on the lunar surface. Close observation of craters, combined with the way the Moon diffusely reflects sunlight, led to the understanding that the Moon is covered by a surface layer, or regolith , that overlies the solid rock of the Moon. Telescopic images permitted the cataloging of a bewildering array of land forms. Craters were studied for clues to their origin; the large circular maria were mapper. Wispy marks on the surface (known as rays) emanating from certain craters were seen. Strange, sinuous features were observed in the maria. Although various land forms were catalogued, the majority of astronomers’ attention was fixed on craters and their origins.
     Astronomers have known for a fairly long time that the shape of craters changes as they increase in size. Small craters with diameters of less than lO-15km have relatively simple shapes. They have rim crests that are elevated above tile surrounding terrain, smooth, bowl-shaped interiors, and depths that are about one-fifth to one-sixth their diameters. The complexity of shape increases for larger craters.
What does the passage mainly discuss?
选项 A、What astronomers learned from the Surveyor and Apollo space missions.
B、Characteristics of the major terrains of the Moon
C、The origin of the Moon’s craters.
D、Techniques used to catalogue the Moon’s land forms.
答案B
解析 主旨判断题。综观全文可知，文章主要解释月球地形形成的特点。因此，B为正确答案。
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