Explanation:

The register responsible for holding the address of the next memory location to be accessed is:

- MAR (Memory Address Register): This register contains the specific memory address that the computer system needs to access for operations such as reading or writing memory data. It plays a critical role in the execution cycle of a CPU.

- IR (Instruction Register) holds the instruction currently being executed.

- MBR (Memory Buffer Register) is used to temporarily hold data read from or to be written to memory.

- DR (Data Register) typically holds operands or results of operations.

Answer: Option 2 - MAR