If someone is a “nativist,” who is he or she against

A nativist is someone who is against immigrants. The nativism movement found its most widespread following during the 1920s following World War I. President Harding ran on a campaign calling for a "return to normalcy," in reference to the internationalist outlook of his predecessor, Woodrow Wilson. Nativists opposed the influx of immigrants and through their efforts led to to passage of the Immigration Restriction Act of 1924.

Cwould be the answer