Final answer:
In Gane and Sarson notation for data flow diagrams, a data flow is represented by a line with a single or double arrowhead, indicating the direction of data movement.
Step-by-step explanation:
In a data flow diagram (DFD) using Gane and Sarson notation, the symbol for a data flow is c. a line with a single or double arrowhead. This line represents the movement of data between processes, data stores, and external entities within the system. The Gane and Sarson notation is one of the visual representations used in structuring system analysis components to show where, how, and when data is stored and moved. Unlike the provided reference items which seem to relate to vector components, the correct answer is solely focused on the representation of data flows in system analysis using DFDs.