One primary school in Britain reads a study on wearing slippers at school. The students at this school decide to wear slippers(拖鞋), too.

The study is more than 10 years long. It covers(覆盖) 25 countries. It says wearing slippers at school is good for students. If students all wear slippers, the classroom are calmer and quieter. At the same time, if students wear slippers, they will do better in exams, and they will also come to school earlier and leave later. Of course, because they stay at school longer, they read more. It also says in some classes, there is less bullying(欺凌行为) because of wearing slippers.

The school likes the change. Some teachers at the school wear slippers, too.

The world itself is becoming much smaller by using modern traffic and modern communication means (工具). Life today is much easier than it was hundreds of years ago, but it has brought new problems. One of the biggest problems is pollution. To pollute means to make things dirty. Pollution comes in many ways. We see it, smell it, drink it and even hear it.

Man has been polluting the earth. The more people have, the more pollution becomes. Many years ago, the problem was not so serious because there were not so many people. When the land was used up or the river was dirty in one place, man moved to another place. But this is no longer true.

Man is now slowly polluting the whole world.

Air pollution is still the most serious. It’s bad for all living things in the world,but it is not the only one kind of pollution. Water pollution kills our fish and pollutes our drinking water. Noise pollution makes us angry more easily.

Many countries are making rules to fight pollution. They stop people from burning coal in houses and factories in the city, and from putting dirty smoke into the air. Pollution by sulfur dioxide (SO₂) is now the most dangerous kind of air pollution. It is caused by heavy traffic. We are sure that if there are fewer people driving, there will be less air pollution.

The earth is our home. We must take care of it. That means keeping the land, water and air clean. And we must pay attention to the rise in pollution at the same time.

We often see ants looking for new homes and returning with other ants if they’ve found a good one. Ants do this by teaching. And a team of scientists have developed small robots to study how ants teach one another. The robots can behave like rock ants. They use one-to-one teaching — an ant discovers a better home and teaches the route (路线) to another.

In their research, the scientists replaced the teaching ant with a small robot. They circled an area with two homes for the ants. One was their old home, and the other was a new, better home built for them. The researchers waited for an ant to leave its old home and put the robot directly ahead of it.

Then the robot moved towards the new, better home. During its journey, the robot stopped from time to time to wait for the follower ant. The ant needed to look around and get familiar with things around it. When the robot led the follower ant to the new home, the ant examined the new home in its own time and began its way back home. The robot had successfully taught the route to the pupil ant.

A key part of the teaching is tandem (纵排的) running. One ant leads another slowly along a route to the new-found home. The pupil ant memorizes the route so that it can find its way back home by itself and then lead another ant to the new home, and the process repeats.