Final answer:
Free variables in a matrix calculator are used to determine the number of variables in a system of equations.
Step-by-step explanation:
The free variables in a matrix calculator are used to determine the number of variables in the system of equations represented by the matrix. These variables represent unknown values in the system, and the number of free variables indicates the number of different ways the system can be solved.
For example, if a matrix has 3 free variables, it means that there are 3 different values that can be assigned to those variables to satisfy the equations.
The correct answer is D) Variables.