What does the command grub-install /dev/sda do?

What does the command grub-install /dev/sda do?

A.
GRUB creates partitions on the device/dev/sdato be used with Linux.

B.
GRUB sets the default BIOS boot device to/dev/sda.

C.
GRUB installs all required files and configures the boot loader on device/dev/sda.

D.
GRUB recompiles the Linux Kernel and installs it on the Master Boot Record of device/dev/sda.