Please help, not sure what this one may be, Thank you!

How is MAR different than MDR? Answer (Multiple Choice): a) MAR contains the address of a memory location, whereas MDR contains the actual data that are stored at that specific memory location. b) OMDR contains the address of a memory location, whereas MAR contains the actual data that are stored at that specific memory location. c) Both MAR and MDR serve the same purpose, namely store memory addresses or data as needed. d) OMAR stores the address of the instruction that is currently executing in the CPU, whereas MDR stores the operands of that specific instruction. Explain your