Music critic: How well an underground rock group' s recordings sell is no mark of that group' s success as an underground group. After all, if a recording sells well, it may be because some of the music on the recording is too trendy to be authentically underground; accordingly, many underground musicians consider it desirable for a recording not to sell well. But weak sales may simply be the result of the group' s incompetence. Which one of the following principles, if valid, most helps to justify the music critic's argument? ['An underground rock group is successful as an underground group if the group is competent but its recordings nonetheless do not sell well.', 'An underground rock group is unsuccessful as an underground group if it is incompetent or if any of its music is too trendy to be authentically underground, or both.', 'For an underground rock group, competence and the creation of authentically underground music are not in themselves marks of success.', "Whether an underground group's recordings meet criteria that many underground musicians consider desirable is not a mark of that group's success."]