What is the quantity to be inspected upon examination for customs?

The correct choice, which suggests inspecting one out of ten items or not less than one per invoice, aligns with standard practices for customs inspections aimed at balancing efficiency with compliance. This approach reflects a systematic and selective examination process, allowing customs officials to maintain oversight while avoiding the impracticality of inspecting every single item.

By focusing on a representative sample rather than conducting a complete inspection of all goods, customs can effectively identify potential issues with compliance or authenticity without overwhelming resources. This method also promotes quicker clearance processes, as customs officers can manage their time and workload more effectively.

The other options do not align as well with the common customs inspection policies. Inspecting all items would be excessive and inefficient, while focusing only on items suspected of being non-compliant may overlook random occurrences of compliance issues. Similarly, inspecting one item for every five invoices does not establish a practical ratio for oversight and could lead to ineffective monitoring practices. Thus, the chosen answer represents a balanced, practical, and widely accepted method for customs inspections.