12. He suggested that a petition (draw) ………… up.
III/ Read the following passage, then choose the best answer:10p
The sun today is yellw dwarf star. It is powered by thermonuclear reactions near its center
that change hydrogen into helium. The sun has existed in its present state for about 4 billion,
600 million years and is thousands of times larger than the earth.
By studying other stars, astronomers can predict what the rest of the sun's life will be
like. About 5 billion years from now, the core of the sun will shrink and become hotter. The
surface temperature will fall. The higher temperature of the center will increase the rate of
thermonuclear reactions. The outer regions of the sun will expand approximately 35 million
miles, about the distance to Mercury, which is the closest planet to the sun. The sun will
become too hot for life to exist.
Once the sun has used its thermonuclear energy as a red giant, it will begin to shrinks
to the size of the earth, it will become a white dwarf star. The sun may throw off huge
amounts of gases in violent eruptions called nova explosions as it changes from a red giant to
a white dwarf.
After billions of years as a white dwarf, the sun will have used up all its fuel and will
have lost its heat. Such a star is called a black dwarff. After the sun has become a black
dwarf, the earth will be dark and cold. If any atmosphere remains there, it will have frozen
onto the earth's surface.
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