Belady's anomaly refers to a phenomenon in page replacement algorithms, where increasing the number of page frames can actually result in more page faults. This anomaly is observed in the FIFO (First-In-First-Out) page replacement algorithm.

Explanation:

FIFO (First-In-First-Out) Page Replacement Algorithm:
- In the FIFO algorithm, the page that has been in memory the longest is replaced when a page fault occurs.
- It maintains a queue of the pages in memory, and the page at the front of the queue is the oldest page.
- When a new page needs to be brought into memory and there are no free frames available, the page at the front of the queue is replaced with the new page.

Belady's Anomaly:
- Belady's anomaly occurs when increasing the number of page frames does not decrease the number of page faults.
- In some cases, increasing the number of page frames may actually result in more page faults.
- This anomaly is observed in the FIFO page replacement algorithm.

Explanation of Belady's Anomaly in FIFO Algorithm:
- Let's consider a scenario where the page references are: 1 2 3 4 1 2 5 1 2 3 4 5
- Initially, let's assume there are only 3 page frames available.
- The page faults occurring with 3 page frames are: 1 2 3 4 1 2 5 1 2 3 4 5 (total 9 page faults)
- Now, let's increase the number of page frames to 4 and repeat the page references.
- The page faults occurring with 4 page frames are: 1 2 3 4 1 2 5 1 2 3 4 5 (total 10 page faults)

As observed in the above example, increasing the number of page frames from 3 to 4 resulted in more page faults. This contradicts the notion that increasing the number of page frames should always reduce the number of page faults.

Therefore, the correct answer is option 'A' - FIFO page replacement algorithm suffers from Belady's anomaly.