Reduction: It means that the way to solve a problem is not direct, but to deform and transform the problem until it is reduced to a certain problem (s) that have been resolved, or it is easy to solve and then return to find the original problem Solution. Which of the following does not belong to reduction? ['Xiao Zhang obtained the sum of the internal angles of the polygon by decomposing the polygon into several triangles.', "Xiao Wu was awkward with Xiao Wen. Xiao Wu wanted to apologize and couldn't let go, and told Xiao Cai the cause and effect. Xiao Cai explained to Xiao Wen. After Xiao Cai explained, Xiao Wu greeted Xiao Wen, and the two were as good as ever.", 'Xiao Li and Xiao Jiang have very different methods to solve the same type of problem. Xiao Li first studies special problems and then general problems, while Xiao Jiang first solves general problems and then studies special situations.', 'Xiao Zhao adopted the principle of easy first and then difficult, and quickly completed a lot of physical assignments assigned by the teacher.']