Final answer:
The correct answer is option A) New immigration laws and the arrival of different ethnic groups.
Step-by-step explanation:
During the Third Wave of immigration, there were significant changes, primarily related to the demographics and societal impacts brought about by the new immigrant populations. Option A) New immigration laws and the arrival of different ethnic groups is the correct answer. This period saw a demographic shift with a surge in immigration from Southern and Eastern Europe, introducing new ethnic groups to the United States. These groups were subjected to intense discrimination and prejudice, which was further exacerbated by the Dillingham Commission's reports confirming ethnic identification and discrimination of these new immigrants.
The Great Migration also played a role during this time, with African Americans moving from the South to urban centers seeking work and a reprieve from racism. These new demographics faced numerous challenges, living in ethnic enclaves within cities, seeking low-paid labor, and enduring hostility from more established groups. The passage of anti-immigration legislation reflected the xenophobic attitudes and discrimination aimed at preserving the ethnic homogeneity perceived to be under threat by these new arrivals.