Which of the following are examples of Linux boot loaders?

GRUB (Grand Unified Bootloader) is the standard bootloader for most modern Linux distributions including Ubuntu, Fedora, and Debian, and is responsible for loading the Linux kernel into memory at startup. It replaced the older LILO bootloader and supports booting multiple operating systems from a single machine. GRUB2 is the current version included by virtually all major distributions.

ILOS is not a Linux bootloader; iLO (Integrated Lights-Out) is Hewlett-Packard's server management firmware interface, entirely unrelated to the OS boot process.

While LILO (Linux Loader) was historically a valid Linux bootloader, it has been deprecated and is no longer shipped by modern Linux distributions, making GRUB the correct answer for current systems.

Ubuntu BootPro is not a real product or recognized Linux bootloader and does not exist in any official Linux distribution or upstream project.