George has made__great progress that he can write an article in English.

so一般修饰形容词或副词，而such和名词及名词短语搭配。这里great progress是一个整体，名词短语，中心词是progress，所以要用such.

你可以看作：such a great progress that，但注意progress是不可数名词,随意要把a去掉。

因为后面有progress这个名词,后面没有名词的时候用so

固定用法：such+(a/an)adj.+n.

当然用such，状语从句，把great progress 看成整体，为名词

so是用来修饰形容词的such能指代后面的名词the progress he made was so great that he can...he made such progress that he can

很重要的语法点：
such a friendly way = so friendly a way
例如：so beautiful a flower = such a beautifal flower
但对于形容量的多少，只有一种：
例如：
so much progress
so many books