Which phrase describes what the "push and pull" theory was about? А.
American Indians in the West
B.
nativism
C. immigrants coming to America
D. political machines in cities

in contrast, the biological controls are self-sustaining, inexpensive and very effective once established. biological control could be used on thousands of golf course acres, improving their biodiversity and quality as wildlife habitat. in the process, the golf industry will be shown to be leaders in an environmental stewardship program of benefit not only to the lands they manage but also to the watersheds in which they exist.

your answer would be (b)