Concept:An abacus is a simple manual calculating tool used for basic arithmetic operations.
Explanation:The abacus is primarily used to perform addition and subtraction.
It helps in counting and calculating quickly by moving beads on rods.
In many schools, it is introduced to teach the basic concepts of addition and subtraction.
Although an abacus can also be used for multiplication, division, and other calculations with practice, its standard and most common classroom use is for addition and subtraction.
Therefore, among the given options, the correct description of its use is "addition and subtraction."
Answer:C. addition and subtraction