The so-called Kingdom of the Congo or Congo Empire was an African region located in southwestern Africa in the territory that today corresponds to the north-west of Angola including Cabinda, the Republic of Congo, the western part of the Democratic Republic of Congo and the south-central part of the Gabon.
Many got attracted to Kongo because of the mines. There were quite a few rich gold mines at Sofala. They were also quite skilled at agriculture, carving, weaving, pottery and many other things.
The rise of the Kingdom of Kongo was that many people got attracted to Kongo because of the rich gold mines at Sofala. Also, they have been pushing intermarriage with the African people to gain favor and pushing farther into the interior of Africa. Aside from that people also developed skills like weaving, pottery, blacksmithing, and carving which have also contributed to their economy. Also, the agriculture was a big part in Kongo.
Most research uses both primary and secondary sources. They complement each other to help you build a convincing argument. Primary sources are more credible as evidence, but secondary sources show how your work relates to existing research.
I would think Christianity because outside of every one of their churches that i ever pass by in my car, There is always a stake,or a wooden cross with Jesus on it.