The correct answer is "set aside lands that had never been inhabited by humans."
To create national parks like Yellowstone, Yosemite, and Glacier, the federal government set aside lands that had never been inhabited by humans.
The environmental policy has been the result of the effort and persistence of many conservationists and the work of the representatives that had approved laws to protect the environment. Local, state, and federal governments have done many things in order to protect natural resources. Through the years, among the many pieces of legislation that protect the environment in the United States are the Clean Water Act, the Clean Air Act, and the Endangered Species Act.