The correct matches are:
Oil - Nigeria;
Nigeria is one of the biggest producers of oil in Africa and that is because it has large reserves of oil on its territory. Big portion of the economy is based on the oil income, unfortunately though the technology used for extraction and transportation is old and there's lot of loses and spills.
Rich soils - Kenya;
Kenya is a country that has suitable rain patterns, rich and vast grasslands, and tropical climate. This has resulted in the country having a very fertile soil. That is largely because of the enormous amount of biomass from the grasses, helped by the rainfall and the high temperatures to decompose quickly.
Mineral wealth - South Africa;
South Africa is a country that is well know for two things, gold and diamonds. It is the country that has the biggest reserves of gold, most of which goes on the foreign markets. Also, it has lot of diamonds, most of which end up sold in their original shape in Western Europe, mostly Belgium.