While testing 10 light bulbs, Harvey finds that 6 of them do not light. Which best describes the fraction of light bulbs that are working? A. number of light bulbs that are not working/total number of light bulbs B. number of light bulbs that are working/number of light bulbs not working C. number of light bulbs that are not working/number of light bulbs working D. number of light bulbs that are working/total number of light bulbs