Which of the following uses hard disk drive space to provide extra memory for a computer?

Virtual memory is an OS memory management technique that uses a designated hard disk area called a page file (Windows) or swap partition (Linux) to store memory pages that do not fit in physical RAM. When RAM fills up, the OS moves inactive pages to disk and loads active pages back into RAM as needed, effectively providing more addressable memory than physical chips alone allow.

A file system is a method for organizing and retrieving data on a storage device - it structures how files are stored but does not function as an extension of system memory.

A cluster is the smallest disk allocation unit a file system uses to store file data - it is a storage concept, not a memory management mechanism.

RAM is the physical memory installed in a computer - it is the primary memory that virtual memory supplements, not the mechanism that uses disk space.