2 a : do you think mr. kim would help me with this project?
b : definitely. he has spent twenty years in the field and has that you would surely find useful.
① many knowledges ② much of knowledge
③ a great deal of knowledge ④ quite a few knowledges
답은 3번이라는데요 2번이 안되는 이유를 알고 싶습니다. much는 대명사로 불가산이 될 수 있지 않나요??