Normally more page frames means fewer page faults. But FIFO page replacement suffers from Belady's anomaly: for some reference strings, increasing the number of frames actually increases the number of page faults.

Example: the reference string 1,2,3,4,1,2,5,1,2,3,4,5 gives 9 faults with 3 frames but 10 faults with 4 frames.

So the effect depends on the memory access pattern.

Answer: (B)