Question

the incas developed a record - keeping system using
shells and beads on strings.
knots and designs in strings.
writing and pictographs.
numbers and calculations.

Explanation:

The Incas used a system called quipu for record - keeping, which involved knots and designs in strings. Shells and beads on strings were not their record - keeping method. They didn't have a traditional writing system with pictographs like some other civilizations, and their record - keeping wasn't mainly about numbers and calculations in the way the option suggests. So the correct option is the one about knots and designs in strings.

Answer:

B. knots and designs in strings.