As viewed from space, the Earth’s distinguishing characteristics are its blue waters and white clouds. Enveloped by an ocean of

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问题     As viewed from space, the Earth’s distinguishing characteristics are its blue waters and white clouds. Enveloped by an ocean of air consisting of 78% nitrogen and 21% oxygen, the planet is the only one in our solar system known to harbor life. Circling the Sun at an average distance of 149 million km (93 million miles), the Earth is the third planet from the Sun and the fifth largest planet in the solar system. Its rapid spin and molten nickel-iron core give rise to an extensive magnetic field which, coupled with the atmosphere, shields us from nearly all of the harmful radiation coming from the Sun and other stars. Most meteors burn up in the Earth’s atmosphere before they can strike the surface. The planet’s active geological processes have left no evidence of the ancient pelting it almost certainly received soon after it was formed. The Earth has a single natural satellite -- the Moon.
The main idea of this passage is that ______.

选项 A、there are life-supporting characteristics on the Earth
B、the Earth is predominantly water
C、the Earth has no common characteristics with other planets
D、the Earth is the only planet with a moon

答案C

解析 概括性的结论是主旨题的答案。而选项A.“地球上有维系生命的特征。”、B.“地球表面主要是水。”、D.“地球是唯一有卫星的星体。”均为具体信息或细节,不能概括全文。选项C.“地球与其他星球有着不同的特征。”则涵盖了全文的信息,并与文中第一句“从太空看,地球与众不同的特征为一有着蓝色的水面和白云。”相吻合。
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