GMAT Sentence Correction (SC) | Re: Ryunosuke Akutagawa s knowledge of the literatures of

Hi Expert,
I need to have this solution too much, because I'm confused about this question pattern! Here is the correctsentence:
Ryunosuke Akutagawa‘s knowledge of the literatures of Europe, China and Japan was instrumental in his development as a writer, informing both his literary style and the content of his fiction.

It seems from the non-underlined part that Europe,China and X (unknown) is not the list of 3 things because there is no COMMA before the final AND. As the correct answer