What is the reason for Belady's Anamoly

Question

What is the reason for Belady’s Anomaly,I am aware that it is not a stack based algorithm and for a certain set of pages it shows this anomaly where the increase in page frame increases the page fault rate.

Answer 1

if pages(m) is  a  subset of pages(m+1) ,where    3 and 4 are frames  then it is stack property

since in fifo we remove the first element from frames set ,which violates the property  and page fault increases so fifo follow belady's analomy