How does your computer maintain its configuration?

The BIOS configurations of our computers are always maintained, even when our systems are powered down and unplugged from a power source. How do our computers maintain their configurations, even when unplugged?

A) CMOS memory can maintain configuration information without power

B) The BIOS configuration of the computer is written to the hard drive and read during the power-up process

C) The CMOS is constantly powered with a small battery on the motherboard

D) The BIOS uses a default configuration each time the computer starts