Final answer:
The Portuguese arrived in the city to establish trade relations, having a history of creating trading networks in West Africa and exerting control over Indian Ocean trade.
Step-by-step explanation:
The Portuguese official and police most likely arrived in the city to establish trade relations. This conclusion is drawn from historical records indicating that the Portuguese frequently established trade networks along the coast of West Africa, where they traded for gold and slaves. They negotiated relationships with local African kingdoms and set up fortresses as trading posts and holding areas for slaves. Additionally, the Portuguese demanded ships trading in the Indian Ocean carry a cartaz, to assert control over trade and increase commerce in Portuguese-controlled ports.