Counting Based Page Replacement Algorithms Are Not Commonly Used, Because

Multiple Choice

Counting based page replacement algorithms are not commonly used, because

A) they only approximate LRU.
B) they are expensive to implement, even though they incur the least number of page faults.
C) they do not approximate OPT replacement very well and their implementation is expensive.
D) they do not approximate OPT replacement very well, even though they are easy to implement.