The correct answer is: A. System’s floppy drive device driver
The system’s floppy drive device driver is responsible for communicating with the floppy drive. If the driver is not working properly, it can cause the problem you are describing. When you remove the drive in question and install it into your test system, and it does not exhibit the problem, this further confirms that the problem is with the driver.
The other options are not likely to be the cause of the problem. The original IDE controller is responsible for communicating with the hard drive, not the floppy drive. The floppy drive ribbon cable is responsible for connecting the floppy drive to the motherboard. The system’s power supply is responsible for providing power to the system, including the floppy drive.
Therefore, the most likely cause of the problem is the system’s floppy drive device driver.