Read the sentence below, which states a main idea.
"The National Park Service preserves places where key events in American history happened."
Which detail supports this main idea?
a) National parks are also used to preserve wilderness areas for Americans to visit.
b) Ellis Island is now a national park with a museum dedicated to the history of immigration.
c) Most Americans think that the National Park Service is about mountains and canyons—not museums.
d) Camping in a national park often feels very rugged because the park buildings are basic.
