@Manu Thakur @rahul sharma 5
Initially, I also thought it should have been "MFU algorithm" but if you consider FIFO then let's take an example of page reference string as : 1,2,3,1,1,1,2,1,1,2,3,1,1,1,4 (3 page frames)
Now if page 4 comes then 1 will be removed.
Here 1 is initialized very early as well as it is in constant use. For LRU and LFU no example will satisfy both conditions.
Please correct me if I am wrong.