The word that can substitute the given group of words "One who does not know reading or writing" is "Illiterate."

Explanation of the options:

☀ Scholar: A scholar is a person who has a high level of knowledge in a particular field and is often engaged in academic or intellectual pursuits.

☀ Illiterate: Illiterate refers to a person who lacks the ability to read or write.

☀ Erudite: Erudite refers to a person who has extensive knowledge or learning, often gained through study or scholarship.

☀ Fastidious: Fastidious refers to a person who is very attentive to and concerned about accuracy and detail, often associated with being overly particular or fussy.