The battery is polarizing

There’s a small round battery on the motherboard of your computer. What function does this battery provide?

A) Provides enough voltage to start the hard drives platters

B) Drives the power needed by the keyboard during the boot process

C) Maintains the computer CMOS BIOS configuration settings

D) Powers the LED lights used on the computer case

E) Plays my hip MP3 collection without starting the computer. Bust a move.