Question 21

Option A: Paging allocates physical memory in fixed-size blocks called page frames. Any free frame can be allocated to any process, eliminating external fragmentation completely. (Correct)

Option B: Internal fragmentation occurs within the last page of a process allocation because memory is assigned in discrete page increments. The expected internal fragmentation per process is roughly half a page size, so page size directly affects internal fragmentation. (Incorrect)

Option C: Paging requires page tables (and multi-level page tables for large virtual spaces) stored in main memory, which introduces both space overhead for table structures and time overhead for translations. (Correct)

Option D: Multi-level paging is introduced to avoid allocating massive contiguous physical memory for sparse linear page tables. It is not necessary to support multiple page sizes (which is handled by architectures via separate page size flags in translation descriptors or TLB entries). (Incorrect)

Thus, statements A and C are correct.