Answer: d. economic activity and development.
Between the 9th and the 15th centuries, small, independent states arose in central and northern Italy. This included cities such as Venice, Florence, Milan, Genoa, Bologna and Verona. These cities went through enormous changes, such as a demographic explosion (the population doubled during this period), an emergence of huge cities (especially Florence, Venice and Milan), migration from country to city (highest rate of urbanization in the world) and the rise of commerce. Commerce in particular flourished because the rulers of these cities did not enjoy the absolute power of other monarchies. Moreover, they were interested in fostering economic activity and development. This created the conditions for the Renaissance to arise.