In the context of an operating system, what is "virtual memory"?

Question $5$ options:

A system allowing different regions or segments of memory to be granted different security privileges

None of the other choices.

All of the other choices $($except "None of the other choices"$)$

A system that translates memory addresses instructions in a process use memory addresses in hardware RAM

A system allowing processes access to a large, contiguous group of memory addresses

A system allowing swapping lesser used sections of RAM to a non$-$volatile storage in low memory situation