What role did the geography of the Sahel play in the rise of the medieval African kingdoms?It provided access to the large ports on the Atlantic. The lack of fresh water made rulers here more warlike. It provided a place for trade between the North and the South. The desert was difficult for outsiders to invade.

b is the answer i am assuming

to extend a country’s power and influence

the causes of the dust bowls were severe droughts,   lands became dry and hard, temperature was higher than usual, hot and dry conditions killed crops, high winds. because of those factors, the winds kicked up dry soil and created clouds of dust.