Listen again and complete the answers to the following questions. 1. How important is the Rhine to Western Europe? It is most important waterway . 2. What happened to the Rhine from the 1950s to the 1970s? It was . Fish disappeared and it was dangerous to swim in it . 3. What happened in 1986? A fire broke out at a chemical plant in Basel, which caused to leak into the Rhi ne . 4. What was the good result of what happened in 1986? The countries along the Rhine realized that they should work together to and keep it clean. 5. How often is the water at various points in the Rhine extracted and checked? minutes, 24 hours a day.