The correct answer is B - large urban areas became even larger.
This is logical when you consider the fact that building aqueducts improved (increased) the water supply of a particular area through which aqueducts were running. This in turn enabled people to more further away from water sources as water was being rerouted through different areas. And when we're talking in terms of large urban areas, this enabled the creation of more and more building in urban areas which increased their size.