A system maintains a fixed-size memory buffer of three items, which is updated by adding the most recent data segment to the end and simultaneously removing the oldest segment from the beginning. Given a previous memory state, Mem_pre = [A, B, C], and a new incoming data segment, S_kv = D, what is the new memory state, Mem, after the update operation is applied?

Sequential FIFO Memory Updates

A system updates its memory using the formula $Mem = \text{FIFO}(S_{kv}, Mem_{pre})$. Match each component of the formula to its correct description in this process.