18. Ultra Realty received a cheque for $21,000 on July 1, which represents a 6-month advance payment of rent on a building it rents to a client. Unearned Rental Revenue was credited for the full $21,000. Financial statements will be prepared on July 31. Ultra Realty should make the following adjusting entry on July 31: A. debit Unearned Rental Revenue, $3,500; credit Rental Revenue, $3,500. B. debit Rental Revenue, $3,500; credit Unearned Rental Revenue, $3,500. C. debit Unearned Rental Revenue, $21,000; credit Rental Revenue, $21,000. D. debit Cash, $3,500; credit Rental Revenue, $3,500