Final answer:
Option B: The working set model for page replacement is based on the assumption of locality. It assumes that programs tend to access a relatively small portion of their address space at any given time.
Step-by-step explanation:
The working set model for page replacement is based on the assumption of locality. Locality refers to the phenomenon where programs tend to access a relatively small portion of their address space at any given time. In the context of memory management, the working set is the set of pages that a program is actively using at a particular moment. This model is used in page replacement algorithms such as LRU.
The working set model assumes that if the working set of a program can be kept in memory, then the program's performance will be good. However, if the working set is larger than the available memory, page faults will occur and some pages will need to be evicted to make space for new ones.
This model is used in page replacement algorithms such as the LRU (Least Recently Used) algorithm, where the least recently used page is evicted when a page fault happens.