Answer:
Of, until, to.
Explanation:
In this sentence we can find three prepositions: of, until, to.
"I never understood the value of studying until I went to college."
How do we know they are prepositions?
We know they are prepositions because they belong to a close class of words and they have little meaning. For example: nouns, verbs, adjectives belong to an open class of words and they have full meaning. Prepositions have a function in the sentence.
