How has Charlie’s understanding of Joe and Frank changed?
in the book flowers for algernon

can you give me a hint

write it down

then read over it

then trun it in

what part is in bold?

many is the pronoun that is used in this sentence. many is a quantifier that determines the amount of discoveries. when we use quatifiers followed by nouns, they act as determiners, but when they are used without a noun, as it is this case, they are pronouns.