3. He didn’t use to be active in school, but now he gets lots of ________.

March 22 is World Water Day. It started in 1993. It not only makes us think about the importance of water, but   also calls on（号召）us to___and protect water. Today, we're facing terrible water problems. Among them, the wastewater problem is rather ___, And the subject of World Water Day in 2017 is “wastewater”.

What is wastewater? It is used water.   Usually, wastewater comes from homes,___, hospital and so on. It is produced by different kinds of activities, including washing machines, taking showers and using kitchens. The rain also___wastewater when it is running down the street during a storm. No matter where it comes from, this kind of water is sure to have____harmful in it．

___must we treat（处理）wastewater? Wastewater has a big influence in our lives. It causes both illness for us and pollution for the environment. We must care for our environment and our own___.

How can we treat wastewater? Different kinds of wastewater need different ways of treatment. Wastewater___homes can be reused. Then there will be___wastewater. Also, factory wastewater has to be cleaned____it goes back to nature.

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 comes. 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 polluted 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 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 all need a healthy environment, but we produce waste every day. It is bad     41     our environment. However, we can do something to help. Recycling is one of the     42    (great) ways to make a difference in the world. It is important for both our natural environment and     43    (we), especially when we can get a little money for doing so.

Mr. Black is our class     44    (teach). He loves to recycle and always encourages us all to take part in it. By recycling bottles, newspapers, and other things, he     45     gets about thirty dollars a month. It is not a lot of money,    46     he is happy to have a little extra(额外的) money now and then. Most of the time he     47    (use) the money to take his family to the cinema. So his family always look forward to     48    (go) to the movies at the end of every month.

Mr. Black also teaches his children the     49    (important) of protecting the environment by recycling. So all the Black family love recycling and they lead     50     meaningful life.