Which of the Following Statements About Program Ratings and Share

Which of the following statements about program ratings and share of audience measures is true?

A) Unlike share of audience measures, program ratings consider variation in the number of sets in use since they are based only on those households that have their sets in use.
B) Program ratings are always higher than share of audience.
C) Share of audience is always higher than the program rating unless all of the households in a market have their set in use.
D) Program ratings and share of audience are usually the same.