The answers are:
A. Sequence of events: Continuum. Like the season of the year, it is something that keeps on going, changing gradually.
B. Ethnic neighborhoods: Enclave. This is a group of people of a specific ethnic character surrounded by neighborhoods of other ethnic characters.
C. Anti-immigrant: Nativist. People that defend the rights of established inhabitants against immigrants.
D. Those in favor of multicultural diversity: Ethnicists. Although the word is rare, it can mean a group of people with an interest in promoting the interaction of different cultures.
E. Oversimplification: Reductionism. To represent a complex phenomenon through other phenomena of a more simplified nature.
F. Renewing a run-down area: Gentrification. Used mostly when referring to the process of renewal according to middle-class standards and interests.
