Purchase order lines represent the agreed scope of goods or services to be delivered and billed, and closing a line signals that no further receiving or invoicing activity is expected, which can also affect budget checks and encumbrance balances. The Official Workday Pro Procure-to-Pay Guide indicates that the appropriate time to close a PO line is once all goods or services on that line have been fully received and fully invoiced, confirming that the line's lifecycle is complete and no remaining activity is anticipated. Option A is incorrect because focusing on whether the supplier invoice has been paid ties the closure decision to the payment process rather than to the completeness of receiving and invoicing, which are the relevant triggers. Option C is incorrect because closing a line immediately after approval would prevent any receiving or invoicing from ever occurring against that line, which contradicts its purpose. Option D is incorrect because tying line closure strictly to fiscal year-end is arbitrary and could result in closing incomplete lines prematurely or leaving completed lines open unnecessarily.