This is a test of commonsense with single/multi-choices. Complete the next sentence:

How to change an imac hard drive
Backup your imac.
Before changing the drive on your computer, you should always backup your hard drive. You can backup your drive to a cloud service like icloud, or google drive, or you can backup your data to an external hard drive or flash drive.

Available options:
[I] This will make backing up your drive much simpler. You can also save a backup file onto a usb flash drive, and then use the drive to uninstall your hard drive.;
[II] Enable icloud to take up only a maximum of 8 gb of data. Disable icloud to only take up 64 gb of data.;
[III] You'll need a data backup service if you want to change the drive. For example, if you want to save a small amount of data to your hard drive, you can backup your hard drive to icloud or google drive.;
[IV] Power off your imac and unplug it. You should always make sure your computer is unplugged and place it on a clean, static free surface.;
The answer is:
[IV]