According to reports, 248 middle schools in a poor area have been synchronizing classes with key middle schools in a certain tier city for 16 years through live broadcast. Over the past 16 years, some of these 248 middle schools have provincial champions and some have undergraduate progression rates It has increased more than tenfold. From the data point of view, this live teaching mode is very successful. However, it is regrettable that this successful mode has not been widely promoted throughout the country. Which of the following, if true, cannot explain this regrettable phenomenon. ['Different middle school students have different knowledge bases, and this live teaching is not targeted.', 'This model requires the concerted efforts of many departments and faces many difficulties.', 'It is difficult to form high-level teachers in middle schools in most poor areas.', 'Some poor areas are backward and conservative, unwilling to try and accept new things.']