听力原文： Unless measures are taken at once, there is a good chance that all the oceans of the world will be heavily polluted by the year 2000. How could this possibly happen? We have already seen that people allow all kinds of waste products to flow into the sea. It is almost impossible to measure how much sewage and industrial waste end up in our oceans. And [low about oil pollution in the oceans? It is illegal to discharge oil into the sea close to the coast, but when a ship is many miles out to sea there are no such restrictions. Sometimes there is a ship collision, and our beaches are covered with oil. But collisions are not the only cause of oil pollution, not even the main cause. Much more oil is discharged at sea when the oil tanks are cleaned out. Estimates of the amount of oil discharged into the sea vary quite a lot, but the lowest figure for oil discharged into European waters alone is about 200,000 tons every year. Some people say that the figure could be ten times higher. It is not only our beaches that are polluted by oil, among other things, some fish in the sea now contain great amounts of poisonous substances. Next time you eat fish, how can you be sure that they are free from oil pollution? It is really quite a problem. (30)