PART C Directions: You will hear three dialogues or monologues. Before listening to each one, you will have 5 seconds to read each of the questions which accompany it. While listening, answer each question by choosing A, B, C or D. After listening, you will have 10 seconds to check your answer to each question. You will hear each piece ONLY ONCE. 听力原文：M: Welcome to Yellow Stone National Park. Before we begin our nature walk today, I'd like to give you a short history of our national park service. The national park service began in the late 1800s. A small group of explorers had just completed a month long exploration of the region that is now Yellow Stone. They gathered around the campfire and after hours of discussion, they decided that they should not claim this land for themselves. They felt it should be accessible to everyone so they began a campaign to preserve this land for everyone's enjoyment. Two years later, in die late 19th century, an Act of Congress signed by President Ulysses S. Grant proclaimed the Yellow Stone region a public park. It was the first national park in the world. After Yellow Stone became a public park, many other areas of great scenic importance were set aside. And in 1916 the national park service was established to manage these parks. As a park ranger, I am an employee of the national park service. In the national park, park rangers are on duty at all times to answer questions and help visitors in any difficulty. Nature walks, guided tours and campfires talks axe offered by specially trained staff members. The park service also protects the animals and plants within the park. According to the speaker, who originated the idea of the public park?