VI, Read the passage and circle the best option A, B, C or D to complete the following questions or
statements:
The Sun today is a yellow dwarf star. It is fueled by thermonuclear reactions near its center that convert
hydrogen to helium. The Sun has existed in its present state for about four billion six hundred 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 five 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 then be a red giant star.
Temperatures on the Earth will become too high for life to exist. Once the Sun has used up its
thermonuclear energy as a red giant, it will begin to shrink. After it 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 dwarf. After the Sun
has become a black dwarf, the Earth will be dark and cold. If any atmosphere remains there, it will have
frozen over the Earth’s surface.
66. It can be inferred from the passage that the Sun ______.
A. is approximately halfway through its life as a yellow dwarf
B. will continue to be a yellow dwarf for another 10 billion years
C. has been in existence for 10 billion years
D. is rapidly changing in size and brightness
67. What will probably be the first stage of change for the Sun to become a red giant?
A. Its surface will become hotter and shrink.
B. It will throw off huge amounts of gases.
C. Its central part will grow smaller and hotter.
D. Its core will cool off and use less fuel.
