Sociologist: Research shows, contrary to popular opinion, that, all other things being equal, most people who have pets are less happy than most people who do not. Ttherefore, any person who wants to be as happy as possible would do well to consider not having a pet. Which one of the following, if true, most seriously weakens the sociologist's argument? ['Most people who have no pets occasionally wish that they had pets.', 'All people who have no pets admit to feeling unhappy sometimes.', 'Most people who have pets feel happier because they have pets.', 'Some people who have pets are happier than most people who do not.']