The conversation between human and AI assistant.
[|Human|] In the sentence, identify which preposition or adverb is used and offer a better alternative.
[|AI|] The preposition used in the sentence is "for." An alternative preposition that can be used is "during." The revised sentence would be: "He studied during hours on end."
[|Human|] 
In the sentence, identify which preposition or adverb is used and offer a better alternative.