Answer:
Slaves.
Step-by-step explanation:
The Kingdom of Kongo extended in the western part of central Africa. Portuguese developed a connection with the Kingdom after meeting King Nzinga a Nkuwu in 1482. Portugal introduces Christianity and baptised Kongo King, that resulted in the foundation of Catholic in the region. The Portuguese began trading in Kongolese slaves immediately after they met people in the kingdom. The relationship between the two became hostile when Europeans demanded more slaves from the African Kingdom.