Đọc đoạn văn và trả lời câu hỏi

         Every nation has areas of natural beauty . These areas almost always contain valuable and interesting plants and animals that often cannot be found anywhere else on Earth . Therefore , these areas must be protected so that they can continue to add to people's enjoyment and scientific knowledge.
         For this purpose dozens of countries in North and South Americans , Europe , Asia , Africa , and the South Pacific have established more than 3.500 national park and other protected areas . Included in these are many nature reserves that have been set aside to conserve a particular kind of plant or animal . A number of countries have also set aside areas or sites of great historical significance.
77. Which title best expresses the ideas in this passage ?
            A. Children's Park                                                        B. Amusement Parks 
            C. Nature Reserves                                                     D. National Park
78. According to the passage , there are _________ main types of national parks 
            A. two                                                                           B. three
            C. four                                                                          D. five
79. The phrasal verb add to in line 3 , paragraph 1, could best be replaced by ____________
            A. bring                                                                         B. create 
            C. increase                                                                   D. change
80. The word these in line 3 , paragraph 2 , refers to_________________
            A. countries                                                                  B. national parks 
            C. nature reserves                                                       D. other protected areas