Step 1: Think of the PCB as a process's identity card.
Just like an ID card carries a person's essential details, the Process Control Block is the data structure the OS keeps for every process, holding everything the kernel needs to manage and later resume that process.
Step 2: List what actually goes on that card.
Typical fields include the process ID, current process state, such as new, ready, running, waiting, or terminated, the program counter, saved CPU register values, scheduling priority, and memory management information. Process ID and process state are two of the most fundamental fields, present in every PCB regardless of the OS.
Step 3: Compare with the distractor options.
Memory addresses of all system files, network configuration settings, and CPU scheduling algorithms are not things a single process's PCB stores, those belong to entirely different subsystems or are OS-wide settings, not per-process data.
Step 4: Settle on the answer.
The option that genuinely reflects PCB content is
\[ \boxed{\text{Process ID and process state}} \]