The correct answer is the motherboard. DDR3 and DDR4 RAM have different physical layouts (pin configurations), voltages, and other features, so they require different memory slots on the motherboard. The CPU, hard drive, and power supply do not directly affect RAM compatibility.
The correct answer is the motherboard. DDR3 and DDR4 RAM have different physical layouts (pin configurations), voltages, and other features, so they require different memory slots on the motherboard. The CPU, hard drive, and power supply do not directly affect RAM compatibility.