Have you ever seen black smoke out of factories, turning the sky a dirty gray? Cars, trucks, buses pollute the air too. Smoke from fires pollutes the air.
Land pollution, water pollution, and even noise pollution are also big problems. Both factories and common families may thoughtlessly dump（倾倒）rubbish and waste on land or in water. When farm chemicals（化学品）that help crops grow sink into the ground and water, they pollute too.
Ocean life isn't safe from pollution. Ships carrying oil sometimes have accidents that dump their oil into the ocean.
Dirty air, or smog, is hard to breathe and makes people and animals sick. Dirty water makes people and animals sick when they drink it or wash or live in it. It also kills plants. If land takes in too much waste, nothing will grow on it, and it becomes unfit to live on.
Most people find it hard to change the way they live, even if they want to. And governments and big factories find it even harder to change, since the changes are often unpopular or costly（代价高的）.
Even small changes help, however. Reusing things instead of throwing them away helps. So does recycling. And perhaps the future will find people using cleaner forms of energy, such as wind power and solar energy.
A. This is air pollution.
B. Stopping pollution isn't easy.
C. Using less water each day helps.
D. Dirty air, water and land are dangerous.
E. Everyone must do something to reduce pollution.
F. You should stay at home to keep away from dirty air.
G. And noise pollution is created by loud machines and cars.
