Answer:
C, She read encyclopedias and other books.
Explanation:
A- We can automtically cross that one out
B- She might have studied at home but she woudnt know what to study since she barely went to school
C- She most likely read books to be intelligent
D- Having a photographic memory is very rare and she wouldn't be able to be intelliegnt if she barely went to school since she doesnt know what is being taught.