Question: In 1872, the United States created a national park called Yellowstone. The park includes more than two million acres in the three states of Idaho, Montana, and Wyoming. Which statement best explains why national parks have a positive effect on ecosystems?

  Options: 
 A. National parks limit people from seeing wildlife.
 B. National parks limit mining, logging, and hunting.
 C. National parks protect land for farmers and ranchers.
 D. National parks protect land for people to build houses.
Answer: B