Which empire did not have a written system for communication? a. incas c. olmecs b. mayan d. aztecs

Among the four empires Incas, Olmecs, Mayan and Aztecs; the Incans are the ones who has no written means of communications. They use fast roadrunners or mailmen called chasqui to relay messages.  Messages were sent oral or by knotted messages called quipu. Incans can deliver messages at a speed of 250 miles/day. 

b. ensure mutual protection from communism.

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