单选题
How many things can you see in the night sky? A lot!
On a clear night you might see the Moon, some planets, and thousands of
sparkling stars. You can see even more with a telescope. You
might see stars where before you only saw dark space. You might see that many
stars look larger than others. You might see that some stars that look white are
really red or blue. With bigger and bigger telescopes you can see more and more
objects in the sky. And you can see those objects in more and more
details. But scientists believe there are some things in the
sky that we will never see. We won't see them with the biggest telescope in the
world, on the clearest night of the year. That's because they're Invisible.
They're the mysterious dead stars called black holes. You might
find it hard to imagine that stars die. After all, our Sun is a star. Year after
year we see it up in the sky burning brightly, giving us heat and light. The Sun
certainly doesn't seem to be getting old or weak. But stars do burn out and die
after billions of years. As a star's gases burn, they give off
light and heat. But when the gas runs out, the star stops burning and begins to
die. As the star cools, the outer layers of the star pull in
toward the center. The star squashes into a smaller and smaller ball. If the
star was very small, the star ends up as a cold. dark ball called a black dwarf.
If the star was very big, it keeps squashing inward until it's packed together
tighter than anything in the universe. Imagine if the each were
crushed until it was the size of a tiny marble. That's how tightly this dead
star, a black hole is packed. What pulls the star in toward its center with such
power?. It's the same force that pulls you down when you jump--the force called
gravity. A black hole is so tightly packed that its gravity sucks in
everything--even light. The light from black hole can never come back to your
eyes. That's why you see nothing but blackness. So the next
time you stare up at the night sky, remember: there's more in the sky than meets
the eyes! Scattered in the silent darkness are black holes--the great mystery of
space.
单选题
According to the article, what causes a star to die?
A. As its gases run out, it cools down.
B. It collides with other stars.
C. It can only live for about a million years.
D. As it gets honer and hotter, it explodes.
【正确答案】
A
【答案解析】[解析] 题目问：根据文章内容，是什么导致了恒星的死亡?第五段“As a star's gases burn, they give off light and heat. But when the gas runs out, the star stops burning and begins to die.”通过这句话可知，当恒星的气体燃烧时，它们放出光和热。但是，当气体耗尽，恒星就停止了燃烧，就开始死亡了。所以，答案是A。
单选题
Which of the following statements is NOT a fact?
A. Black holes are dead stars.
B. Black holes have gravity,
C. Black holes are invisible.
D. There is nothing as mysterious as a black hole.
【正确答案】
D
【答案解析】[解析] 题目问：下列哪项不是事实?“They're the mysterious dead stars called black holes.通过这句话可知。黑洞是死的星星。What pulls the star in toward its center with such power? It's the same force that pulls you down when you jump-the force called gravity.”通过这句话可知，黑洞有重力。“That's because they're invisible.”通过这句话可知。黑洞看不见。“Scattered in the silent darkness are black holes--the great mystery of space.”通过这句话可知。黑洞是寂静宇宙中最神秘的。所以，答案是D。
单选题
Why can't you see light when you look at a black hole?
A. Because most black holes are so far away.
B. Because the gravity of a black hole is so strong that it sucks the light
inward.
C. Because as the star's gases burn, it stops giving off heat and
light.
D. Because as a star cools, its outer layers pull in toward its
center.
【正确答案】
B
【答案解析】[解析] 题目问：当你看到一个黑洞时，为什么你不能见到光?倒数第二段“A black hole is so tightly packed that its gravity sucks in everything--even light. The light from black hole Can never come back to your eyes. That's why you see noting but blackness.”通过这段话可知，黑洞是如此的紧凑。以至于它的重力吸收一切东西。甚至是光。黑洞里的光永远也到不了你的眼睛里。这就是你为什么看到一片漆黑的原因。所以，答案是A。
单选题
What is the main idea of the article?
A. The future of our Sun billions of years from now.
B. The difference between our Sun and a dead star.