Concept:A subroutine in a flowchart is represented by a symbol that stands for a separate, pre-defined set of steps.Explanation:When a subroutine is called, it is not usually drawn fully inside the main flowchart.Instead, it is shown using the predefined process symbol.This symbol is drawn as a rectangle with extra vertical lines on its left and right sides.It indicates that the actual steps are defined elsewhere and are simply executed at that point.So, calling a subroutine means using the predefined process symbol in the flowchart.Answer:B. predefined process