The register in the 8085A that is used to keep track of the memory address of the next op-code to be run in the program is the:

ANS:B - program counter

Instruction pointer (IP).

Intel's term for the register that points to the next instruction to fetch. Actually, at Intel it is properly the pair CS:IP, code segment and instruction pointer, but since Intel's 8086 and 80286 era segments are deprecated the term IP by itself will often be used.

Program counter (PC).

Another popular term for the register that points to the next instruction to fetch.

The meaning of both IP and PC is extended beyond that register to the address, the contents of the register. E.g. we may say "the instruction has IP=...."

Up until the late 1990s I would estimate that the term PC was more common than the term IP for essentially the same concept. But with the dominance of Intel in the 1990s and 2000s, the term IP may have become more common.