Final answer:
The true statement about the Data Flow Diagram is that arrows, which represent data flows, must have both a source and a destination. Data can flow from various elements in the diagram, not just from a data store, and the inclusion of external entities depends on the level of the DFD.
Step-by-step explanation:
The statement concerning the diagram 1.0 logical data flow diagram (DFD) that is true is: b. An arrow should never leave a bubble with no destination. In a DFD, each data flow must have a source and a destination. Data flows are represented by arrows, and they cannot just float without being connected to either a process (which are represented by circles or 'bubbles'), a data store, or external entities. A data store, depicted by two parallel lines, shows where data is held within the system. While a data flow can originate from a data store, indicating data retrieval, it is incorrect to state that data should only flow from a data store. Finally, though higher-level DFDs typically include external entities to demonstrate how the system interacts with outside elements, the level of detail required regarding external entities can vary depending on the level of the DFD.
Regarding other diagrams mentioned:
- A diagram discussing the flow of goods and payments between firms and a foreign country relates to economics, specifically international trade, and would be part of a circular flow model.
- Free-body diagrams are a concept in physics. They represent the forces acting on an object, helping to visualize and calculate the net force. Drawing free-body diagrams is not the last step but one of the initial steps in solving physics problems involving forces.