Concept:The operating system is the main software that controls the computer and makes it able to start up.
Explanation:Booting is the startup process that loads the operating system into the main memory.
Without the OS, the computer hardware has no instructions to begin running.
A compiler, loader, or assembler are not required for the computer to start.
A compiler translates program code, an assembler converts assembly language, and a loader places programs into memory.
These tools only help with programming tasks, not with the boot process.
Only the operating system provides the basic control needed for booting.
Therefore, if the OS is absent, the computer cannot boot.
Answer:C. OS