My fist is as hard as a rock.
Simile
Metaphor
Idiom
Allusion

line a --> main

line b --> young

line c --> atitude

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.

may i ask on your question is there any word specific that is bolded or are they wanting us to figure it out?