Correct Answer: is possible only when the register is an accumulator or instruction register

Solution : The correct option is is possible only when the register is an accumulator or instruction register.

Writing new data into a register is only feasible if the register is an accumulator or instruction register. A register used to hold operands for arithmetic and logical operations is known as an accumulator. It is also utilised to keep track of the outcomes of these processes. An instruction register is a register that contains the current instruction that the CPU is executing. This is due to the CPU's requirement to manage the flow of data through the system. It would be difficult for the CPU to keep track of what data is where and what is expected to happen to it if any register could be written to at any moment. The CPU may guarantee that data is only written to when it is needed and when the CPU is ready to process it by restricting writing to accumulators and instruction registers.