阅读下列短文，从每题所给的A、B、C、D四个选项中选出最佳选项。
A
Into the Wild
— Get to know some of the mammals that call Yellowstone home
Bison
Bison can weigh up to 2,000 pounds and are herbivores(食草动物). Despite their size, they are very mobile and can run up to 30 mph and jump up to six feet vertically. In1902, America's wild bison had decreased to only two dozen due to overhunting. Conservation efforts increased the Yellowstone bison population to 4,800 in 2023. See them in Hayden, Lamar and Pelican valleys.
Gray Wolf
Gray wolves had gone extinct in Yellowstone until 14 were reintroduced in 1995. Today, approximately 108 wolves live here. These social animals live in groups and can be gray, white or black. They hunt elk, deer and bison near dawn and dusk thanks to their excellent night vision. For your best chance of seeing them, head to Lamar or Hayden valleys or Blacktail Deer Plateau in the early morning.
Elk
Up to 20,000 elk summer in Yellowstone, but most move to lower elevations in the winter months. Elk are a large member of the deer family and can be identified by their size and white rumps. Mating season, known as“ the rut”, occurs each fall when male elk fight with each other for females. It's characterized by their haunting bugling sound. In the summer, see them in Cascade Meadows, Madison Canyon and Lamar Valley.
Grizzly Bear
One of two species of bears in Yellowstone, grizzlies are big. They can weigh up to700 pounds and have a distinctive hump between their shoulders. Grizzlies are omnivores and will eat bugs, plants, fish and mammals. Approximately 150 live in Yellowstone and if you' re lucky, you may spot them in the Hayden and Lamar valleys, north of Mount Washington and between Fishing Bridge and the East Entrance.
21. What contributed to the decline of America’s wild bi son population by 1902?
A. Disease. B. Climate change.
C. Unsustainable hunting. D. Habitat loss.
22. Which of the following statements is TRUE about gray wolves in Yellowstone?
A. They were reintroduced in 1902.
B. They primarily hunt during the midday.
C. They can only be found in Lamar Valley.
D. They live in packs and can have various colors.
23. Where are you most likely to encounter all the four mammals in Yellowstone?
A. Lamar Valley. B. Madison Canyon.
C. Pelican Valley. D. Hayden Valley.
