Error C. The word "conform to the world trend" is too broad. Note that the question asks the most fundamental reason. All the changes in the modern scientific and cultural system are influenced by the world trend, but according to the view of history textbooks, this is not the most fundamental reason.

D. Western advanced science, technology and culture poured in in large quantities. As early as the Opium War, western science and technology and culture had already walked in front of China. The reform of the education system, the establishment of schools, the abolition of the imperial examination, the establishment of the academic system, etc. were all things around the beginning of the twentieth century. This is not the most fundamental reason.

By the way, A. The educational reform at that time did not win many people's hearts. First of all, at that time, ordinary people couldn't even write, and it made no difference to them whether they changed or not. However, Confucian scholars who used to rely on the imperial examination for fame and fortune, as well as those who are old-fashioned, are very opposed to the new education system.