On Dec.9，three Chinese astronauts gave a science lecture 400 kilometers above Earth!Zhai Zhigang，Wang Yaping and Ye Guangfu who are working aboard the Tiangong space station，showed our students a glimpse of their life there.They also did some fun science experiments.Let's take a look at some of them.

Use it or lose it

The human body grows with the pull of Earth's gravity （重力）.But in space，our bones and muscles （肌肉） don't need to support our body's weight.This will cause bone and muscle loss.It's reported that astronauts can lose up to 20% of their muscles after just a couple of weeks.That is dangerous for astronauts because they will be too weak to work.

Astronauts have different ways to prevent this.During the lecture，Zhai introduced a special uniform Ye was wearing.It's called a "penguin suit".There are many elastic bands（弹力带）inside the suit.Wearing it，astronauts use their muscles to stretch（拉伸） the bands.This keeps their muscles strong.Wang also showed students how she walked on a treadmill （跑步机） and rode a bicycle.Astronauts exercise with these tools every day to prevent muscle loss.

Space water is different

Water in space acts differently from water on Earth in other ways.For example，water will not flow（流动） downward if you try to pour it into a cup.That's why astronauts usually drink water through straws（吸管）in sealed（密封的）bags.If astronauts cry，the tears will stay on their eyeballs instead of falling down.They have to wipe（擦拭）them away！

During another experiment，Wang made a water film （膜）.Then she added more water drops onto the film to make it a water ball.This can never happen on Earth.

（1）The astronauts gave a 　 　lecture 400 kilometers above Earth on Dec.9.

A．	science
B．	Chinese
C．	history
D．	geography

（2）The astronauts might become weak in the space because 　 　.

A．	their bodies will stop growing
B．	they have to work for long hours
C．	they might lose some of their muscles
D．	their muscles have to support more weight

（3）Zhai showed 　 　to the students during the lecture.

A．	Earth's gravity
B．	a "penguin suit"
C．	a treadmill
D．	a bicycle

（4）Which is NOT TRUE about water in space？ 　 　

A．	If astronauts cry，the tears will stay on their eyeballs.
B．	If astronauts pour the water into a cup，it will flow downward.
C．	If astronauts add more water drops onto the film，it will become a water ball.
D．	The astronauts usually drink water through straws in sealed bags.

（5）The word " 　 　" can best describe the lecture in space.

A．	Boring
B．	Careless
C．	Dangerous
D．	Eye﹣opening