[C]. a planetoid (small planet) created when a meteorite, upon striking the moon, breaks off a part of the moon.
[D]. a dark spot on the moon, once supposed to be a sea, now a plain.
2. The writer does not believe that
[A]. an asteroid is larger than a meteorite.
[B]. material from space, upon hitting the earth, was eventually distributed.
[C]. the earth, at one time, had craters.
[D]. ocean were formerly craters.
3. The article is primarily concerned with
[A]. the origin of continents.
[B]. the relationship between astral phenomena and the moon.
[C]. differences of opinion among authoritative geologists.
[D]. the relationship between asteroids and meteorites.
4. Sialic material refers to
[A]. the broken rock resulting from the impact of a meteorite against the earth.
[B]. material that exists on planets other than the earth.
[C]. a composite of rock typical of continental areas of the earth.
[D]. material that is man-made to simulate materials that existed far back in geological history.
答案祥解
1. D. 是月球上的一个黑点,一度认识是海,现在知道是平原。Mare basin海盆地。词义本身说明D项对。另一方面,第二段开始提及鲍德温所列出的月球上最大的陨石坑直径为285公里。可是,如果我们接受了某些由于撞击而形成海盆地的结构假设,那么月球上最大陨石坑的直径可能有650公里大。这里都说mare basin指的是月球上陨石坑。这就排除了A,B,C三个选项。
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