The correct answer is "D"
In the 15th century, when the Portuguese colonized the archipelago of Cape Verde, the islands did justice to their name: they were covered by dense tropical vegetation, which contrasted with their black volcanic rocks and the blue sea. There is no evidence that they were populated before the arrival of the settlers, but it is considered probable that the Arabs had visited the island of Sal in previous centuries to provide themselves with that substance. In 1462, the first Portuguese settlers landed in what is now Santiago and founded the oldest European city in the tropics: Ribeira Grande (now Cidade Velha). The Portuguese introduced the cultivation of sugarcane, but the dry climate was not favorable. So they were mainly dedicated to the slave trade, mainly from the west coast of Africa. The rise of slavery revolutionized Cape Verde's economy in just a few years. While in 1506 it was one of the Portuguese possessions in Africa that provided the least income to the Crown, by 1510 it had become the second most rented, only surpassed by the Gold Mine.