Final answer:
The physical data flow diagram is the one that specifically indicates where, how, and by whom a system's processes are performed, by detailing the system's real-world implementation and resources involved.
Step-by-step explanation:
The type of data flow diagram that specifies where, how, and by whom a system's processes are performed is the physical data flow diagram. Unlike a logical data flow diagram, which focuses on the flow of data and the processes without considering how they are implemented, a physical data flow diagram gives more insight into the actual implementation of the system. It details the concrete elements like the specific hardware, software, files, and people involved in the processes.