Final answer:
The adjusting entry for this scenario is to debit Insurance Expense $600 and credit Prepaid Insurance $600.
Step-by-step explanation:
The adjusting entry in this scenario would be option d. Debit Insurance Expense $600; Credit Prepaid Insurance $600. This entry would ensure that the insurance expense for the month of October is properly recognized by debiting Insurance Expense and offsetting it with a credit to Prepaid Insurance, reducing the balance.