Can you make animals work for us? Some scientists think that one day we can teach animals to do a lot of things for people. In a film shown on TV, you may see elephants, monkeys, tigers or some other animals are always given a little food to eat after they have done something. Scientists say that people can teach many different animals to do some of the easy work if they know they will get something to eat. We all know elephants can carry large logs(圆木)，and dogs can look after houses. And we even teach animals to work in factories. In America, for example, people have used apes to help make cars and scientists think that those large monkeys may drive trains one day. Now people are trying to get them to do the same thing that man does.
【小题1】Scientists think animals can help people to do something _____ .

Can you imagine astronauts' everyday life in space? They also need to eat,  sleep, exercise and relax. They do the same things as us, but they do them differently.
On Earth, we put food on a plate. Gravity holds the food down and keeps it on a place. But there is almost no gravity in space, so food can float （漂浮）away, and astronauts must eat carefully.
Sleeping is very different in space. Some astronauts like to float in the air, but most like to be in a sleeping bag. They tie the bag to a wall so that they won't float away at night.
Exercise is very important in space. On Earth,  your legs carry your body,  but in space, astronauts float, so they do not use their legs often. This is very bad for their legs, so they must exercise for thirty minutes every day.
After a day's work, astronauts relax. They may listen to music, read, watch films, play games, or talk to their friends and families on the radio. Sometimes they just enjoy floating in the air.
【小题1】What does the underlined word "gravity" mean in Chinese?

Can you imagine astronauts' everyday life in space? They also need to eat,  sleep, exercise and relax. They do the same things as us, but they do them differently.

On Earth, we put food on a plate. Gravity holds the food down and keeps it on a place. But there is almost no gravity in space, so food can float （漂浮）away, and astronauts must eat carefully.

Sleeping is very different in space. Some astronauts like to float in the air, but most like to be in a sleeping bag. They tie the bag to a wall so that they won't float away at night.

Exercise is very important in space. On Earth,  your legs carry your body,  but in space, astronauts float, so they do not use their legs often. This is very bad for their legs, so they must exercise for thirty minutes every day.

After a day's work, astronauts relax. They may listen to music, read, watch films, play games, or talk to their friends and families on the radio. Sometimes they just enjoy floating in the air.

1.What does the underlined word "gravity" mean in Chinese?

2.Why do astronauts tie the sleeping bag to a wall?

3.What's the main idea of the passage?