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  3. It is always hard for a small fish to live in a big pond. Pluto’s recent departure from the classical planet family clearly prov

It is always hard for a small fish to live in a big pond. Pluto’s recent departure from the classical planet family clearly prov

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问题     It is always hard for a small fish to live in a big pond. Pluto’s recent departure from the classical planet family clearly proves that size really matters.
    Astronomers voted on August 24 to give a definition to the word "planet", and Pluto turned out to be only a " dwarf planet"(矮行星). After weeks of heated debate, over 2, 500 astronomers from 73 countries voted on the definition of a "planet" at a conference of the International Astronomical Union(IAU). According to the definition, a planet must have a clear neighborhood around its orbit. Pluto has widely been considered a planet since its discovery in 1930. Unfortunately, it has a special orbit which overlaps with Neptune’s. It is all because, compared with Neptune, Pluto is very small. It is attracted by Neptune’s gravity when the two planets get closer.
    According to IAU, a "dwarf planet" should have an orbit around the sun. It will not have a clear neighborhood a-round its orbit, and must not be a satellite. The new classification means that the science textbooks will have to be updated. The solar system is now made up of the eight "classical planets", together with a number of dwarf planets. The classical planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Astronomers sent an advanced telescope into space, and found a belt of objects, which lies beyond Neptune. The belt contains nearly 1, 000 objects, including Pluto. As they continued the exploration, scientists recendy discovered at least 41 dwarf planets at the edges of the solar system. There are at least two objects of a similar size to Pluto.
    It seems that even if the IAU had kept Pluto’s status as a planet, the classical theory of nine planets in the solar system would have had to be changed. More dwarf planets of a similar size to Pluto would join the family of planets. Scientists will probably find many more dwarf planets.
The sentence "It is always hard for a small fish to live in big pond" quoted at the beginning of the passage is used to______.
选项 A、tell us small fish can hardly survive in the big pond
B、tell us the size of an object really matters
C、mean that small planet can hardly exist in the solar system
D、explain the disappearance of Pluto in the solar system
答案B
解析 文中第一段第二句提到，冥王星脱离行星家族证明了天体的体积的重要性。
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