A、It urges campers to treat its service with respect. B、It urges campers to love the nature. C、It shows respect to the nature. D

Imagine a night sky so full of brilliant stars that you can actually point out them to your kids. Meat stuck on sticks, bubbling over a campfire. It’ s easy to envision the ideal camping experience—but not everyone has actually experienced it. If your best recollection of camping is frozen toes, a mattress and a large rock in the middle of your back, take heart! Camping has changed, and there’ s something for everyone.
    Camping can teach you many things, such as how to recognize plants and animals, to set up a tent and to read a map. Most of all, you can anticipate understanding more about yourself and your place in nature.
    Whether you decided to travel on foot into the wilderness, to travel by canoe, or simply to drive to a nearby camp ground, you are probably looking for some of the same experiences. Most campers hope to find a simpler lifestyle. They tend to forget about work and worries while they enjoy being outdoors.
    Because the number of the U.S. campers is increasing daily, the National Park Service advises outdoor lovers to remember several things. First, although it encourages campers to enjoy the outdoors, it urges everyone to treat nature with respect. That involves leaving your campsite cleaner than you found it. It involves learning to enjoy the natural world of plants and animals without disturbing it. Remember that wild animals are wild, and they can hurt you, just as you can hurt them.
    The park service invites you to enjoy and explore the world of nature, but at the same time, it expects you to protect each area you visit so that future generations may look forward to having similar enjoyable experiences.
Questions 19 to 21 are based on the passage you have just heard.
19. What is the main purpose for camping?
20. What do most campers look for?
21. What does the National Park Service urge the campers to do?