Many people use relative location on a daily basis by using B) their mental maps of an area.
You know what a certain area looks like, at least approximately, so you don't need to use these other options on a day to day basis. You can rely on your mental maps to do the work for you.
The answer is C, ROM often stores the basic instructions a computer needs when powering on, part if the BIOS.
Answer: Y2K bug, also called Year 2000 bug or Millennium Bug