a new car is old with or without anti-lock brakes, with or without a CD player, with or without electric seats, and with or without a sunroof. How many different choices are there?
I think you want the number of subsets given 4 different sets
number of subsets = 2^4 or 16, which includes the null set
that is, a car having none of the 4 options listed
and a car having all 4 of the options listed.