Read the passage below before answering the question.
Return of the American Bison
In the early 1800s, tens of millions of bison roamed the Great Plains of North America, including the vast grasslands of South Dakota. However, by 1890, over-hunting brought the species close to extinction, with fewer than 1,000 animals remaining. Recognizing the crisis, conservationists and Native American tribes established protected reserves like Custer State Park and Badlands National Park. Today, thanks to careful breeding and habitat protection, over 500,000 bison live in North America, restoring balance to the prairie ecosystem.
What caused the American bison population to drop severely by 1890?
- AOver-hunting brought the bison close to extinction.
- BA massive asteroid hit the Great Plains.
- CAll bison migrated across the ocean to Europe.
- DSevere flooding covered all prairie grass in deep water.