A. Use computers in right ways.
B. How to sleep in space
C. The importance of exercise
D. Signs and messages
E. Eating and drinking in space
1.(   )As we know, we put food on a plate and water in a glass on earth. Gravity(地心引力) holds the food down and keeps the water in the glass. But in space, there is almost no gravity. So food can float away, and astronauts must eat and drink carefully.
2.(   )In space, sleeping is very different. Some astronauts like to float in the air, but most astronauts like to be in a sleeping bag. They tie the bag to a wall so that they can’t float at night.
3.(   ) 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. This is bad for their legs, so they exercise for thirty minutes every day. They often use an exercise bike for this.