hidernation : what drive the file will be?

Somebody asked me the following question:
Booting from C-drive (primairy partition) windows will be started from logical partition D (rootdirectory d:\winnt). Pagefile.sys has been put on logical drive E. If system will hibernate, what drive will hiberfill.sys be located?

I'm not sure about the answer.
I think it will be C-drive as to me it seems logical that file has to be on the bootdrive (because driveorder can be changed if other disks will or will not be mounted onto the PC as well and being on the bootdrive it will be found for sure if it exists).

I found one site (http://www.helpwithwindows.com/windowsxp/tune-11.html) telling this about hibernation:
"What you need to know is that if hibernate is enabled on your computer, a hidden file hiberfill.sys is created in the root of your system drive (usually C:\), which is around the same size as your system's memory (RAM). You can't move this file to another drive, it has to be in the root of your system drive "

This answer is not fully satisfying as WHAT SYSTEM is meant EXACTLY by 'system drive'? Is it the drive windows is located (D-drive in my case) or is it the drive being booted from (C-drive)?

Does anybody know the definitive answer to my question?

 

C: is your system drive, D: is your boot drive.
You will have Hiberfil.Sys file with a size of less than 1kb located on C:, and a Hiberfil.Sys file with a size equal to installed ram on your D: drive.