I feel, to be precise, "Paging" performs translation from program's address space into physical memory address space. So its "paging that implements the translation of a program's address space into physical memory address space". Not virtual memory. Thus option A also sounds incorrect. Yes sometimes the address space as perceived by process/program is called logical/virtual address space. But then that is different concept from virtual address space that refers to the secondary memory space (part of HDD) that behaves like main memory (RAM). So actually, both options A and D sound incorrenct. Am I right?