Final answer:
When a void function is called, it is known as an executable statement.
Step-by-step explanation:
A) a returned value. B) a comment. C) an executable statement. D) an output function.
When a void function is called, it does not return a value, so option A is incorrect. A comment is not a function call, so option B is incorrect.
An executable statement is a line of code that performs an action, and when a void function is called, it is an executable statement.
Therefore, option C is the correct answer. Option D, an output function, is not necessarily related to void functions, so it is an irrelevant choice.