HELP PLEASSSEEE

Which is a valid conclusion that can be drawn from the fact that many large cities in the United
States still have areas called "Chinatown", "Little Italy", and "Germantown"?

a. some areas of large cities are physically isolated from the rest of the city

b. before becoming citizens, immigrants must live in specified areas of large cities

C. most immigrants assimilated quickly into the culture of the United States

d. ethnic groups often try to preserve their cultural heritage