Which of the Following Commands Overwrites the Bootloader Located on /Dev/sda

Multiple Choice

Which of the following commands overwrites the bootloader located on /dev/sda without overwriting the partition table or any data following it?

A) dd if=/dev/zero of=/dev/sda bs=512
B) dd if=/dev/zero of=/dev/sda bs=512 count=1
C) dd if=/dev/zero of=/dev/sda bs=440 count=1
D) dd if=/dev/zero of=/dev/sda bs=440