2. 自考
  3. When we accept the evidence of our unaided eyes and describe the Sun as a yellow star, we have summed up the most important sing

When we accept the evidence of our unaided eyes and describe the Sun as a yellow star, we have summed up the most important sing

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问题     When we accept the evidence of our unaided eyes and describe the Sun as a yellow star, we have summed up the most important single fact about it at this moment in time. It appears probable, however, that sunlight will be the color we know for only a negligibly small part of the Sun’s history.
    Stars, like individuals, age and change. As we look out into space, we see around us stars at all stages of evolution. There are faint bloodred dwarfs so cool that their surface temperature is a mere 4,000 degrees Fahrenheit, there are searing ghosts blazing at 100,000 degrees Fahrenheit and almost too hot to be seen, for the great part of their radiation is in the invisible ultraviolet range. Obviously, the "daylight" produced by any star depends on its temperature; today (and for ages to come) our Sun is at about 10,000 degrees Fahrenheit, and this means that most of the Sun’s light is concentrated in the yellow band of the spectrum, falling slowly in intensity toward both the longer and shorter light waves.
    That yellow "hump" will shift as the Sun evolves, and the light of day will change accordingly. It is natural to assume that as the Sun grows older, and uses up its hydrogen fuel—which it is now doing at the spanking rate of half a billion tons a second — it will become steadily colder and redder.
What is the passage mainly about? (  )
选项 A、Faint dwarf stars.
B、The evolutionary cycle of the Sun.
C、The Sun’s fuel problem.
D、The dangers of invisible radiation.
答案B
解析 主旨题。“这篇文章主要讲述什么?”B选项“太阳的变化循环”。文章第一段…that sunlight will be…the Sun’s history，整篇文章围绕太阳随时间变化的一些特征论述。A选项“暗淡的小行星”；C选项“太阳的燃料问题”；D选项“不可见的放射危险”。这几项均不是文章最主要的内容。
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