The correct answer is exclusion.
Nativists were a group of individuals who disliked immigration. Nativists felt that immigrants were harmful to American society, as many of them were willing to work for less than unskilled workers from the United States. This fear of losing jobs to immigrants as well as worrying about these new immigrants trying to change American culture resulted in the development of a strong anti-immigration group in the United States.
Nativist ideas/policies would help to shape American laws from the late 1800's to the early to mid 1900's.