﹩12﹣visitors 16and older entering by bike，ski，etc．

This fee provides the visitor with a 7﹣day entrance permit for the Yellowstone National Park．

A﹩50park annual pass provides entrance for a single private non﹣commercial vehicle at Yellowstone National Park．The﹩10Interagency Senior Pass（62and older） is a lifetime pass available to U．S．citizens or permanent residents．

Interesting Yellowstone National Park Facts：

◇A designated World Heritage Site and designated Biosphere Reserve

◇World's First National Park

◇3,472square miles or 8,987square km

◇2,221,766acres or 898,317hectares

◇63air miles north to south（102km）

◇54air miles east to west（87km）

◇96% in Wyoming

◇3% in Montana

◇1% in Idaho

21.Yellowstone National Park is famous for the following except　　．

　A. its wildlife preserves B. its hot springs

　C. its Rocky Mountain scenery D. its noncommercial vehicle

22.Two college students who visit Yellowstone National Park by bike have to pay　　．

　A.﹩50 B.﹩40 C.﹩24 D.﹩20

23. According to the passage，Yellowstone National Park is　　．

　A. the largest designated vulture reserve

　B. the world's first national park

　C. a park with an area of 8，987miles

　D. the only national park in America．

　　B

　　Have you wondered why different animals or pests have their particular colours? Colours in them seem to be used mainly to protect themselves.

　　Birds, especially seagulls are very fond of locusts(蚱蜢), but birds can't easily catch locusts because locusts change their colours together with the change of the colour of crops. When crops are green, locusts look green. But when crops are ripe, locusts take on exactly the same brown colour as crops have. Some other pests with different colours from plants are usually easily found and eaten by their enemies. So they have to hide themselves in terror for lives and appear only at night.

　　If you study the animal life in any part of the world, you will find the main use of colouring is to protect themselves, bears, wolves and other beasts move quietly through forests. They are usually invisible to the eyes of hunters, because they have the colour much like the barks(树皮) of trees.

　　An even more strange act remains to be noticed. A kind of fish living in seas can send out a kind of very black liquid when it faces danger. While the liquid is over, its enemies cannot find it, and it quickly swims away. Thus, it has existed up to now though it is not powerful at all.

24. This passage mainly talks about ______.