Plants have these because root nodules<span> are formed when nitrogen fixing bacteria called "rhizobia" start to enter the cells of a host </span>plant<span>. Rhizobia normally live inside of the soil and they </span>can<span> exist without a host </span>plant<span>.</span>
The natural resources in Ghana,Mali and Songhai contributed most to the growth and power of these empires.
•It brought about the beginning of the trans Saharan Caravan Trade in the 13th and 14th centuries.The gold-salt trade in Africa made these empires very powerful since they controlled the trade routes and taxed traders
•Cities also developed in Ghana,Mali and Songhai because their resources were in high demand and the overland trade routes connected them to west Africa
•The T.S.T brought about the spread of Islam throughout west Africa. The Muslims also sold their commodities (textiles,beads,camels and others) in exchange for gold and salt
I Think The answer is b I hope it helps ya
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