What time is it? What day is it? What hard drive is this?

Every time you start your computer, it complains that the configuration is invalid and the date and time is reset back to defaults. What is the most likely cause of this issue?

A) The BIOS needs to be upgraded

B) The power supply is faulty

C) The computer’s battery needs to be replaced

D) The motherboard is faulty

E) The computer is only pretending not to know what day it is