Describes the process resulting from blacks pushing into contested space in northern cities.

Black Sub-urbanization:

During, the era between 1910 to 1970, most of the black community in the south migrated towards the northern cities.As there were settlements in the northern city made by the black people. About 3.5 million black people were settled in the northern cities, in the era of 1970. As the small towns where black once lived in small number were now considered as cities,due to the large number of black community in the south.

Explanation:

Space in the Northern cities:

Over, 12 metropolitan areas were now occupied by the blacks who migrated to the North. As there was space left by the white people who left the area, but there were many difficulties faced by the black people who migrated to the Northern region. Now, there were two types of black settlements which were been made in the Northern region, which were as follow:

The people who migrated to the neighbor states or region, as they settled inside the Northern cities. And covered most of space.But they faced some issues relating racial slurs from the white community in the northern cities. As the black people faced great difficulties in having a peaceful and prosperous life in the region.While, the other type of Sub-urbanization was done by covering the vacate space or land near the well developed black communities in the Northern region.So, they made extension into those land and covered them up for making a more densely covered area or we can say a metropolitan region in the North.

Ithink the answer to that would be b):

Answer the use of flood plains and irrigation;