Which, According to the Text, Is One of the Factors

Which, according to the text, is one of the factors that explain the surge of urban revitalization and gentrification?

A) Today, economic factors, including commuting costs, the costs of heating, cooling and financing a home, may be cheaper in the central city.
B) Demographically, there has been an increase in traditional, two-parent families with children, which is more ideally suited to inner city living.
C) Improvements in the urban infrastructure (water, sewer, streets, etc.) have encouraged more families to move back to cities.
D) High quality of inner city schools and educational programs has stimulated movement back into the cities.