Answer: (iii) Replacement algorithms

Explanation:
In cache mapping (especially set-associative and fully-associative), a miss with no empty block requires evicting an existing block. The policy that decides which block to evict is the replacement algorithm.

• FIFO (First-In First-Out): Evicts the block that has been in cache longest (oldest load), using a queue per set. Simple to implement, but not always efficient (does not consider locality).
• LRU (Least Recently Used): Evicts the block least recently accessed, exploiting temporal locality. Most effective general policy; approximates optimal. Implemented via counters/linked list or $n$-way LRU bits. Higher hardware overhead.

Why not other options:

• (i) Mapping techniques: Direct, Associative, Set-Associative - decide where a block can be placed.
• (ii) Addressing techniques: Way of forming addresses.
• (iv) Write policies: Write-through / Write-back (and Write-allocate) - handle consistency between cache and main memory on writes, not eviction.

Hence FIFO and LRU belong to replacement policy class; choice directly affects miss rate and hit ratio.