what are the three characteristics of urban?
['Size: As a rule, in the same country and at the same period, the size of an urban community is much larger than that of a rural community. ... ', 'Density of population: ADVERTISEMENTS: ... ', 'Family: ... ', 'Marriage: ... ', 'Occupation: ... ', 'Class extremes: ... ', 'Social heterogeneity: ... ', 'Social distance:']