Immigrants affect urban environments in all of the following areas except a. cultural behaviors b. city language c. architecture d. the formation of exclaves

I think that the best answer is D. the formation of exclaves, as exclaves are political entities that are inside of another entity. Thus for example an Indian exclave in Bangladesh is a piece of India of Bangladesh. The assignment of territory to one or the other country is not influenced by immigrants. 

African americans at the time just came out of slavery and needed money to provide for there families. so they joined for the money mainly.