When Henrietta Leavitt discovered the period-luminosity relationship, she used Cepheid variable stars that were all located in the Large Magellanic Cloud (LMC). It was (easier / more difficult ) to compare Cepheids in the LMC rather than those located in the Milky Way Galaxy because they are all ( about the same distance away / located at widely varying distances from Earth ). As a result ( differences in apparent brightness are directly related to differences in intrinsic brightness of these stars / all of these stars have the same Doppler shift / all of these stars have the same proper motion )