20. Consider the following page reference string: 1, 2, 3, 4, 2, 1, 5, 6, 2, 1, 2, 3, 7, 6, 3, 2, 1
Assuming there are 4 page frames available and that all frames are initially empty, what is the total number of
page faults that would occur for the page reference string above if the least-recently-used (LRU) replacement
policy is used?
(A) 6 (B) 7 (C) 9 (D) 10 (E) 11
