Final answer:
A data flow diagram shows how data acts through an information system without detailing program logic or processing steps, important for system analysis and design.
Step-by-step explanation:
The diagram that shows how data acts through an information system but does not show program logic or processing steps is a data flow diagram (a). Data flow diagrams (DFDs) are used to visualize the movement of data within a system, without getting into the specifics of program logic or processing steps. This makes DFDs highly effective for analyzing the structure of different systems, ensuring that data gets from one point to another as intended.
Unlike other diagrams like data models, data structures, or data trees, data flow diagrams prioritize the pathways and destinations of information. They are especially useful in the preliminary stages of system design, to gain a clear understanding of how data should interact and flow between different components or processes.