What role did geography play in the rise of the three great west african empires: ghana, mali, and songhai?

The empires of Ghana, Mali and Songhai were located in areas that were conducive to the development of great empires. These empires covered a large extension of land with very different weather and ecosystems, including the Sahara desert and the thick jungles south of the Niger River. The fact that the empires had been established in such diverse locations meant that they had an availability of natural resources that translated into wealth. Moreover, the empires benefitted from the trans-African trade, having an open route to the markets of Europe and the world.

a and c?

i think it is a and c