I believe the answer is: B-it was located at a crossroad for trade between Asia and Europe
This location massively contributed to the vast amount of wealth that the Constantinople made through trading. Commodities from Asia such as spices and silk could be sold at a really high margin to the consumers in European Empires.
It would be "(A) Institution of a secret ballot" that was not part of the Populist Party’s platform, since the Populists were largely about transparency--both within government and big business.
Rome, Milan, Naples, Turin, Bari etc