Final answer:
Option (c), The Accounts Payable department updates the vendor accounts with each purchase transaction to maintain accurate records of what the company owes to its vendors.
Step-by-step explanation:
The department that will immediately adjust the vendor account for each purchase transaction, ensuring that the company knows the correct amount owed to the vendor, is C. Accounts Payable. The Accounts Payable department is responsible for processing vendor invoices and recording the amounts owed to vendors for the goods and services that a company receives.
This includes updating the vendor accounts every time a purchase is made, so the company's financial records accurately reflect its liabilities.