填空题

Going to the beach is many Americans’favorite activity. In the area near New York City, nine million people used to go to the beach every summer. They went swimming in the ocean without giving a thought to what was underwater. But those days are long gone.
In the summer of 1988. the government was forced to shut down beaches all over America. Many of the beaches had to be closed because garbage from hospitals was found in the water. The garbage included glass bottles with samples of blood, and people were afraid they might get AIDS from the blood. Where the medical garbage came from is anybody’s guess. At some beaches, sewage (生活污水) was found in the water.
Americans were shocked by this state of affairs. They had long taken for granted that oceans were big enough to stay clean, even if garbage and sewage were dumped into them. People didn’t think of the underwater garbage because it was out of sight.
Some of the most polluted waters still look beautiful at first glance. San Francisco Bay is a good example of a beautiful bay that’s full of chemicals. Scientists discovered pollution in some lakes and rivers when they found fish with rotting skin. In many parts of America, people are told not to eat too much fish because of pollution.
Most American cities put their garbage in the ground. But New York and a few other cities put their garbage in the ocean. Boston Harbor is so polluted that scientists say it won’t recover until the next century at best. The city of Boston puts its sewage in the water. The government has ordered the city to build a sewage treatment plant.
Cleaning up oceans won’t be easy, but people can no longer ignore this challenge.
If fish live in polluted waters people should not ______.