Which power management mode stores data on the hard drive?

The correct answer is hibernate, as this power management mode is designed to save all the current state of the computer to the hard drive before completely powering down. This allows the machine to turn off completely without losing any open applications or documents. When the computer is turned back on, it can restore the previous session exactly as it was, retrieving the saved data from the hard drive.

In contrast, the sleep mode puts the computer into a low-power state while maintaining the current session in RAM. This allows for quick resumption but does not save the data to the hard drive, meaning if there is a power loss, the unsaved work could be lost.

Standby is very similar to sleep; it uses minimal power while keeping the session in memory. It also does not write the data to the hard drive, thereby making it less secure in case of power interruptions.

As for Pillow.exe, this does not relate to any recognized power management mode and may refer to a joke or fictional program, contributing no functionality in the context of power management.

Thus, hibernate is the mode that specifically writes data to the hard drive, providing a complete shutdown and preserving the user's session efficiently.