— Must we clean the classroom now?

— No, you needn't. It _____ after school.

A. may clean　　 　　　 B. must clean　 　　　 C. need be cleaned　 　 D. can be cleaned

A habit is any action that we have performed so often that it becomes something that we do almost without thinking. Some of them are thought to be bad habits. People spend countless hours and dollars each year trying to get rid of these bad habits but often fail. Why? Change is hard work and there is no shortcut to achieve it. However, there is still some advice for you to follow.
First, look at why you do it. In other words, what’s the result of doing this thing? If your bad habit is shouting at people when you are unhappy or under pressure, what do you get from it? It may make you feel a little better for the moment. Or maybe you have a bad habit of leaving your homework undone. The result could be that you get more time to spend on the Internet!
Next, take a look on the other hand. What are you losing because of your habit? Shouting at other people is a bad habit because it makes people around you feel bad and unhappy. Leaving your homework undone is a bad habit because you may be punished by your teacher. Having more Internet time means that you are losing the chance to learn the things that you need to learn. When you think that way, you’ll find that it’s not wise to keep your bad habit! Now it is time to make a decision. What will you choose? I’m sure you will choose to do what you think is more important.
【小题1】From the first paragraph we know that __________.

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?