Contrast techniques. First write about the difficult experience of studying in the past, and then write about the superior conditions for today's Tai students to study, and then explain that if there is a lack of professionalism or lack of morality, it is mainly due to one's own lack of professionalism, not the fault of others. The contrast is clear and the words are smooth. Leda, quite convincingly, demonstrated his diligence in studying through comparison.