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Thread: toefl 2002-

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    toefl 2002-

    Questions 10-19
    No two comets ever look identical, but they have basic features in common, one of the
    most obvious of which is a coma. A coma looks like a misty, patch of light with one or more
    tails often streaming from it in the direction away from the Sun.
    Line At the heart of a comet's coma lies a nucleus of solid material, typically no more than
    (5) 10 kilometers across. The visible coma is a huge cloud of gas and dust that has escaped
    from the nucleus, which it then surrounds like an extended atmosphere. The coma can extend
    as far as a million kilometers outward from the nucleus. Around the coma there is often an
    even larger invisible envelope of hydrogen gas.
    The most graphic proof that the grand spectacle of a comet develops from a relatively
    (10) small and inconspicuous chunk of ice and dust was the close-up image obtained in 1986 by
    the European Giotto probe of the nucleus of Halley's Comet. It turned out to be a bit like a
    very dark asteroid, measuring 16 by 8 kilometers. Ices have evaporated from its outer layers
    to leave a crust of nearly black dust all over the surface. Bright jets of gas from evaporating
    ice burst out on the side facing the Sun, where the surface gets heated up, carrying dust
    (15) with them. This is how the coma and the tails are created.
    Comets grow tails only when they get warm enough for ice and dust to boil off. As a
    comet's orbit brings it closer to the Sun, first the coma grows, then two distinct tails usually
    form. One, the less common kind, contains electrically charged (i.e., ionized) atoms of gas,
    which are blown off directly in the direction away from the Sun by the magnetic field of
    (20) the solar wind. The other tail is made of neutral dust particles, which get gently pushed back
    by the pressure of the sunlight itself. Unlike the ion tail, which is straight, the dust tail
    becomes curved as the particles follow their own orbits around the Sun.

    14. It can be inferred from the passage that the nucleus of a comet is made up of
    (A) dust and gas
    (B) ice and dust
    (C) hydrogen gas
    (D) electrically charged atoms
    I choose A but the answer is B. WHich is correct? thanks

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    Re: toefl 2002-

    B is correct because they say it is The best way to prepare for exams is not to try and justify your answers but to understand why their answers are the correct ones.

    The nucleus is at the heart of the coma (line 4). The visible coma is a cloud of gas and dust which has escaped from the nucleus (lines 5-6). The spectacle develops from a small chunk of ice and dust (line 10).

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