a company has earned $4000 balance in unearned revenue on its unadjusted trial balance. at the end of the year the company has earned all but one-forth of the revenue. the adjusting journal entry necessary at year end would include a. a debit to service revenue of $4000 b. a credit to unearned revenue for $3000 c. a debit to unearned revenue for $3000 d. a credit to service revenue of $1000