Final answer:
The auditor's examination of sales invoices for supporting documents relates to the audit objective of occurrence, verifying the validity of the recorded sales transactions. Option b.
Step-by-step explanation:
When an auditor examines sales invoices for supporting documents as a test of control, the relevant transaction-related audit objective is occurrence option b. This objective relates to determining whether the transactions recorded actually took place and are valid. In the context of examining invoices, if supporting documents such as shipping documents or signed sales orders are in place, they provide evidence that the sale indeed occurred and the transaction was not fictitious.
Other transaction-related audit objectives such as accuracy involve checking if the transactions are recorded at the correct amounts, classification verifies whether transactions have been recorded in the appropriate account and with the correct expense or revenue category, and timing ensures the transactions are recorded in the correct accounting period.