Which of the following file should be edited, if MBR on /dev/hda is corrupted?

Which of the following file should be edited, if MBR on /dev/hda is corrupted?

A.
/boot/grub/grub.conf

B.
/etc/grub/grub.conf

C.
/etc/grub.conf

D.
/sbin/grub-install/dev/hda