The great rift valley is home to many villages and settlements in africa because

The great rift valley in Africa is home to many villages and settlements in Africa mainly because of two reasons:

1.  The great rift valley has slight climatic modifications from it's surrounding area. It makes life easier for people. It affects the vegetation and animals in a positive manner, thus making food more available. Also there's a rainy season affected by the monsoons and it keeps the water supply on much steadier level.
2. The soil is of better quality then the surrounding area, which makes agriculture flourish and people can rely on themselves in big portion of their food needs.

Why you put last one a? i think is b.

Empty quarter and sandy desert