Final answer:
Virtual memory allows processes to use more memory than is physically available by using disk storage to simulate additional RAM. Threads within a single process share the same virtual memory, but it is processes that are the primary entities sharing this resource.
Step-by-step explanation:
The concept of virtual memory allows a computer to compensate for physical memory shortages by temporarily transferring data from random access memory (RAM) to disk storage. This process enables a system to run applications that require more memory than is physically available. When it comes to sharing via virtual memory, it is processes that typically share this resource. Each process is given the illusion that it has access to a large, contiguous block of memory. This memory does not necessarily exist in physical RAM, but can be backed by the system's hard drive, which is slower, hence it is called 'virtual'. Within a single process, threads share the same virtual memory space allocated to their parent process. Thus, while threads inherently have access to the same virtual memory as they run within processes, it is ultimately processes that virtual memory allows to operate as if they have more memory at their disposal. In summary, the correct is a) Processes.