According to statistics, compared with liberal arts graduates, science and engineering graduates earn more when they first start their jobs. Therefore, high school graduates should apply for science and engineering majors if they want to earn higher income after graduation. What would most weaken the conclusion? ['The proportion of liberal arts students who ultimately earn high income is higher than that of science students.', 'Science and engineering majors are difficult to graduate due to the difficulty of knowledge.', 'Many young people are more willing to choose a profession according to their interests.', "Some people who haven't studied college eventually became famous entrepreneurs."]