The Congo and Niger rivers have interesting irregular courses, and instead of going just in a certain direction, they circle around big areas. This is due to the shape of the landscape, and also because of the types of rocks in the surrounding areas where these two rivers flow.
The shape of the landscape is crucial in the course of a river, since every river is moving through the lowest parts where there isn't obstacles, so these rivers have followed that pattern and it turned out to give them irregular course. Also, the types of rocks on their way are very important, so these rivers managed to get through the sediment rocks as they are easy to erode, but haven't been able to break through the igneous rocks that are much harder.
Igneous rock and metamorphic rock.
Answer: The answer is C.
Explanation: Soil includes 40-45 percent inorganic matter, 5% organic matter, 25% water, and 25% air. The right combination of air, water, minerals, and organic matter is essential for plant life to thrive. Microorganisms (both dead and alive) and decaying plants make up humus, the organic stuff in soil.
