The statement that most correctly analyzes how the cartaz system represented a departure from previous patterns of trade is: "Portuguese ports now had exclusive control of Indian Ocean trade."
The cartaz system was a trading license that the Portuguese implemented to exert control over trade in the Indian Ocean. By requiring all merchant ships to obtain this license, the Portuguese aimed to monopolize the lucrative spice trade and other resources in the region, marking a significant shift from earlier, more open trading practices that had allowed various regional and international traders, including Muslims and Venetians, to operate without such control.