Answer:
A. Is the page-replacement algorithm most often implemented.
Step-by-step explanation:
This algorithm is used when a page that is not present in memory is called, leading to the Operating System to replace one of the existing pages with the needed one. There are different replacing algorithms in order to decide which page will be replaced.
This algorithm is implemented to reduce the number of failures and provide a better funcionality and speed the process by discarding pages that won't be used for a long period of time.