Final answer:
Storing numeric data in variables allows for easier reference and modification of data within a program, enabling clearer and more flexible code.
Step-by-step explanation:
Storing numeric data in variables within a program is advantageous for several reasons. The correct answer to the question "Why is it a good idea to store numeric data in variables in a program?" is D. Because that makes it easier to reference and make changes to the data. Using variables allows programmers to write code that is easier to read and understand, as the variable names can be descriptive of the data they hold. This makes it significantly simpler to locate specific pieces of data and to modify them if necessary throughout the program.
Moreover, variables give a program the flexibility to handle data that may change over time. It is important to note that variables also facilitate the implementation of algorithms that perform computations on the data, as they can be easily manipulated arithmetically and passed into functions and procedures.