On Dec. 9, 2021, three Chinese astronauts gave a science lecture 400 kilometers above Earth. Zhai Zhigang, Wang Yaping and Ye Guangfu, who are working abroad the Tiangong space station, showed millions of students 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. But in space, our bones and muscles don’t need to sustain our body’s weight. This will cause bone and muscle loss. NASA says that astronauts can lose up to 20 percent of their muscles after just a couple of weeks. That is dangerous 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 inside the suit. Wearing it, astronauts use their muscles to stretch the bands. This keeps their muscles strong.

▲ .

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

We need to first understand the surface tension of water. It is like a “skin” of water. The “skin” is there because water molecules are drawn to each other. Most of the time, gravity is too strong and it breaks the “skin”. But with zero gravity in space, the “skin” stays strong and the water ball will not break.

Water in space acts differently from water on Earth in other ways. For example, water will not flow downward if you try to pour it into a cup. That’s why astronauts usually drink water through straws in sealed bags.

【小题1】What can we learn about the lecture from space?

A．It is a part of the astronauts’ daily work.

B．It took place in the Tiangong space station.

C．It is one of the astronauts’ ways to ask for help.

D．It took place 500 kilometers above Earth.

【小题2】What does the underlined word “they” in the passage refer to?

A．astronauts

B．muscles

C．bones

D．bodies

【小题3】Which of the following is the best to fill in “ ▲ ” in the passage?

A．Space water is valuable	B．Space water is different
C．Space water is important	D．Space water is common

【小题4】What’s the writer’s purpose in this passage?

A．To raise people’s interest in space exploration.

B．To explain the importance of space experiments.

C．To ask readers to do more science experiments.

D．To introduce the space lecture given by Chinese astronauts.