Final answer:
Variables are the option to use when inserting placeholders for data that might change.
Step-by-step explanation:
The correct option to insert placeholders for data that might change is c) Variables.
Variables are used in programming languages to store and manipulate data. They can hold different values and can be updated or changed during program execution.
For example, in a program that calculates the average of three numbers, you can use variables to store the values of those numbers and perform calculations using those variables.