In the sentence, identify which preposition or adverb is used and offer a better alternative.
He studied for hours on end.
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."
Complete the following task based on the instruction and optional input provided.### Instruction:
In the sentence, identify which preposition or adverb is used and offer a better alternative.

### Input:
He studied for hours on end.

### Output:
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."