Which control structure is guaranteed to run only one time?

The correct choice is a function call. A function call is designed to execute a block of code singularly each time it is invoked, regardless of the conditions or control mechanisms that might exist outside of the function. This means that each time the program calls the function, it runs through its instructions only once, completing all specified actions within that call before returning control back to the point of invocation.

In contrast, an if statement can execute zero or one time depending on whether the associated condition evaluates to true. Both the do-while loop and for loop are iterative structures that will repeat their code blocks multiple times based on their conditions; the do-while loop will run at least once but may continue based on the post-condition check, whereas the for loop iterates based on its defined range. Therefore, they do not guarantee a single execution like a function call does.