Final answer:
None of the guidelines about DFDs stating that there should only be one process, data store, data flow, or external entity are correct; a DFD is expected to have multiple instances of these to accurately depict the system's information flow.
Step-by-step explanation:
None of the statements regarding the data flow diagram (DFD) guidelines mentioned are correct. According to the principles of a DFD, it is not limited to having only one process, data store, data flow, or external entity. In fact, DFDs are expected to have multiple instances of these components to accurately represent the flow of information within a system or process. A DFD should provide a clear, high-level visualization of the system, including various external entities that interact with the system, multiple processes that data may pass through, various data stores where information is held, and multiple data flows that depict the movement of information from one part to another.
The correct guideline for a data flow diagram (DFD) is that it should have only one process. A process represents a transformation or activity on data, and having multiple processes in a DFD helps to show the flow of data through different stages. Multiple data stores, data flows, and external entities can be present in a DFD, depending on the complexity of the system being modeled. These elements help to represent the different inputs, outputs, and storage of data.