What made florence thrive financially?

Florence was the site of many economic developments. It was witness to new systems of taxation and borrowing during the Middle Ages and the Renaissance. Trade was a major source of economic success. Moreover, industry was strong due to the implementation of craft guilds. Florence was not dominated by royal courts, like other states. Instead, it was a republic with an elected government. This made the city more frugal in taste, which also meant that the behaviour of people in terms of wealth accumulation and saving was more moderate and humble, contributing to the thriving economy.

it would have to be gasioline

the correct answer is b, "fertility rates are increasing, so populations will grow more quickly in the future."