What was the main cause of the islamic world's hardships during the thirteenth century?

a.
western europeans invading muslim lands

b.
mongol tribes invading muslim lands

c.
dissension between rival factions of islam

d.
famine and diseases introduced from africa

The answer is B. Mongol tribes invading Muslim lands.

Explanation:

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the language dates from the contacts of arabian traders with the inhabitants of the east coast of africa over many centuries. under arab influence, swahili originated as a lingua franca used by several closely related bantu-speaking tribal groups.