C．Liquid is lightweight.

　　 D．Astronauts are in great need of water.

　　解析：细节理解题。根据第三段可知选B。

　　答案：B

　　3．We can infer from the passage that astronauts

　　______.

　　 A．drink from cups and glasses

　　 B．always wear diapers in space

　　 C．can move freely during landing

　　 D．must pay attention to the crumbs in space

　　解析：推理判断题。根据第五段的Floating crumbs could get stuck in equipment or an astronaut's eyes.可知，飘浮的碎屑会粘到设备上或宇航员的眼睛上，故推断D项正确。

　　答案：D

　　4．What is the passage mainly about?

　　 A．Astronauts' hard life in space.

　　 B．How astronauts go to the bathroom.

　　 C．The various foods astronauts eat in space.

　　 D．How astronauts eat and deal with waste in space.

　　解析：主旨大意题。本文主要讲了在太空宇航员怎样吃东西和处理垃圾。故选D。

　　答案：D

　　B

　　On a clear night you might see the Moon some planets and thousands of sparkling stars. 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 towards the centre. The star squashes into a smaller and smaller ball. If the star was very small the star