Why is disk$-$swapping an effective technique for enabling efficient use of limited physical memory?

Why is disk$-$swapping an effective technique for enabling efficient use of limited physical memory?

Approximately $90\%$ of code and data is infrequenly used or accessed, allowing it to be paged out to disk.

It allows page tables to be written out to disk, thus allowing for flat page addressing.

Processes are free to use physical memory as persistent backing of their data.

Because in the memory hiearchy, disks outperform physical memory.

All of the above.