Which of the following statements is true about variables in programming?

The statement that variables must be declared before they are used is a key aspect of many programming languages, particularly those that are statically typed. In such languages, declaring a variable involves specifying the variable's name and data type before you can assign a value to it or use it in expressions. This process helps the compiler understand how much memory to allocate and what operations are valid for that variable.

In dynamic programming languages, although variables can often be used without explicit declaration, it is still considered a good practice to initialize them before use to avoid potential errors. The requirement for variable declaration reinforces the importance of clarity and organization within the code, which aids in debugging and maintaining the program.

Thus, the necessity of declaring variables before their use is foundational in programming, establishing rules that guide how data is stored, manipulated, and accessed throughout the program's lifecycle.