Only cadres learn legal knowledge; I am not a cadre, so I don't need to learn legal knowledge. Which of the following inferences is most similar to the above inference structure? ['If you fail the exam, you cannot enter Nanjing University to study; Zhang entered Nanjing University to study, so Zhang passed the exam.', 'As long as the exam passes, you can enter Nanjing University to study; Zhang fails the exam, so Zhang cannot enter Nanjing University to study.', 'Only after passing the exam can he enter Nanjing University; Zhang fails the exam, so Zhang cannot enter Nanjing University to study.', 'Only after passing the exam can he enter Nanjing University; Zhang has passed the exam, so Zhang can enter Nanjing University to study.']