Who used khipu, a system of recording numbers by tying knots on strings?.

The Inca people used them for collecting data and keeping records, monitoring tax obligations, properly collecting census records, calendrical information, and for military organization. The cords stored numeric and other values encoded as knots, often in a base ten positional system.

the answer is c     : )

explanation:

i don't have an explanation because i don't know, but i think the answer is c because i googled it and google is right : ) just kidding google isn't allways right but the answer is still c. i hope this !

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