Final answer:
The correct adjusting entry on December 31 for Fragmental Co. is a debit to Unearned Rent and a credit to Rent Revenue for $3,075, representing three months of earned rental income.
Step-by-step explanation:
The adjusting entry made by Fragmental Co. on December 31 would be a debit to Unearned Rent and a credit to Rent Revenue for the amount of rent that has been earned during the year. As the lease began on October 1 and the rent is $1,025 per month, for three months (October, November, December), the earned amount would be $3,075.
Therefore, the correct adjusting entry on December 31 would be a debit to Unearned Rent and a credit to Rent Revenue for $3,075. This reflects the revenue recognition principle, which states that revenue should be recognized in the accounting period in which it is earned.