Job burnout: refers to the phenomenon that the work itself requires too much of an individual's ability, energy, and resources, causing the worker to feel exhausted. According to this definition, which of the following is not the teachers' job burnout? ['Mr. Wang finds it difficult to complete the extra teaching tasks assigned by the school.', 'Now many students are very naughty and some young teachers are struggling to cope with it.', 'Because Mr. Li often works overtime recently, he has always been weak in class these days.', 'Mr. Zhang has been distressed at work recently because of her tense relationship with her husband.']