In GRUB’s configuration file you find the line

root (hd1,4)

What is corresponding device name on a Linux system?

A.
/dev/hda4

B.
/dev/hda5

C.
/dev/hdb4

D.
/dev/hdb5

Explanation/Reference:
Grub starts counting harddrives and partitions at zero, thus (hd1,4) is the 5th partition on the second harddrive /dev/sdb5 or /dev/hdb5