Thirty years ago, Lake Ponkapog in Hartwell, New Jersey, was full of life. Many birds and animals lived beside the water, which was full of fish. Now there are few birds, animals, and fish. The lake water is polluted. It is in a colour of dirty brown, and it is filled with strange plants. How did this happen? First, we must think about how water gets into Lake Ponkapog. When it rains, water comes into the lake from all around. In the past, there were forests all round Lake Ponkapog, so the rainwater was clean. Now there are many homes around the lake. People often use the chemicals  in their gardens. They use other chemicals inside their houses for cleaning and killing insects. There are also many businesses. Businesses use chemicals in their machines of shops. Other chemicals fall onto the ground from cars or trucks. When it rains, the rainwater picks up all the chemicals from home and businesses and then carries them into the lake . They pollute the water and kill the animals. Boats on the lake are also a problem. Lake Ponkapog is a popular place for motorboats . But oil and gas from boats often get into the lake. So more bad chemicals go into the water this way. People in Hartwell are worried . They love their lake and want to save it. Will it be possible? A clean lake must have clean rainwater going into it. Clean rainwater is possible only if people are more careful about chemicals at home and at other chemicals on the ground. And they mustn't use motorboats any more on the lake. All these may change people's lives. Only then can Lake Ponkapog be a beautiful, clean lake again. To save Lake Ponkapog, people need to   _  .
be more careful about chemicals use the water grow fewer plants in the gardens use more motorboats on the lake