Which statement correctly distinguishes a process from a thread, and how concurrency relates to parallelism?

• A. A PROCESS has a separate address space; a THREAD shares memory within a process; CONCURRENCY is overlapping execution; PARALLELISM is simultaneous execution.
• B. A PROCESS shares memory; a THREAD has a separate address space; CONCURRENCY is overlapping execution; PARALLELISM is sequential execution.
• C. A PROCESS is always a single thread; a THREAD runs an entire program; CONCURRENCY is irrelevant to PARALLELISM.
• D. A PROCESS has a separate address space; a THREAD shares memory; CONCURRENCY refers to hardware speed; PARALLELISM refers to software threading.

Answer: (B)

Understanding how processes and threads differ and how concurrency relates to parallelism starts with memory boundaries and execution timing. A process has its own separate address space, which isolates its memory from other processes. Within that process, multiple threads share the same address space, allowing them to access the same data easily and communicate efficiently. Concurrency is about overlapping or interleaved progress of tasks in time, which can happen on a single core through time-slicing or across multiple cores. Parallelism, on the other hand, means actual simultaneous execution of tasks, typically when multiple cores or processors are involved. So the best statement describes a process with a separate address space, a thread that shares memory within that process, concurrency as overlapping execution, and parallelism as simultaneous execution. Some descriptions mix up who shares memory or equate concurrency with hardware speed, which doesn’t fit how these concepts actually work.