听力原文：W: How was your trip to the Grand Canyon? M: It was excellent! We spent five days hiking along the Colorado River and exploring the side canyons. It was great to get out of the city and back to nature. W: I have only been to the Grand Canyon on a day trip. Did you need to make any special preparations to camp at the bottom? M: We wanted to get into the back country away from the tourists, so we had to get a wilderness permit. W: Was that difficult? M: No. We just went to the ranger station and told them what we wanted to do. They talked to us about where we wanted to go and how long we wanted to stay. They are really just trying to make sure that you know what you are doing and that you have the proper gear. They also give you information on the various trails through the park and educate you about wildlife and park conditions. From what I understand, every year tourists gat sick or die from dehydration. The park officials want to make sure that you have a good canteen full of water before you leave. W: I know what you mean. People often try to do these things without first educating themselves about the dangers. Last year, I went to Nepal with some friends. We trekked to the base of Mount Everest. I had read that altitude sickness was a real problem, so I hired a local porter to help carry things to the higher elevations. Despite the thin air, one of my friends tried to carry his stuff by himself, and he ended up getting really sick. I guess it pays to know what you are doing. (20)