Which of the following need not necessarily be saved on a context switch…

The correct answer is: Translation lookaside buffer (TLB).

During a context switch, the operating system must save the process state required to resume execution later. This includes registers such as the general-purpose registers and the program counter.

The Translation Lookaside Buffer (TLB) is different. It is a hardware cache of recent virtual-to-physical address translations. TLB entries are tied to an address space and can become invalid when switching to another process.

Therefore, the TLB is usually flushed, invalidated, or managed with address-space identifiers, and the new process builds its own TLB entries as it runs. It need not necessarily be saved as part of the process context.