Teacher:This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.
Teacher: Now, understand the problem? Solve this instance: Passage: Although the rivers and coast of this area were among the first places colonized by the Portuguese, who set up trading posts in the 16th century, they did not explore the interior until the 19th century. The local African rulers in Guinea, some of whom prospered greatly from the slave trade, controlled the inland trade and did not allow the Europeans into the interior. They kept them in the fortified coastal settlements where the trading took place. African communities that fought back against slave traders also distrusted European adventurers and would-be settlers. The Portuguese in Guinea were largely restricted to the port of Bissau and Cacheu. A small number of European settlers established isolated farms along Bissau's inland rivers. Question: When did the Portuguese first set up trading posts in Guinea-Bissau?
Student:
16th century