what is the operating system all about ?

May 2012
Operating system is:
a. A collection of hardware components
b. A collection of system software
c. A collection of input-output devices
d. None of the above

what would be the correct answer for above multiple choice question ? explain it also....... :?
Dec 2007
It's a collection of system software which allows you to fully make use of your computer's hardware. Examples of operating systems are Windows and Linux.