Final answer:
The headline using standards as a trade barrier is "Only professionally cleaned oranges allowed in US." Such standards can restrict imports, similar to import quotas, and protect domestic prices and industries.
Step-by-step explanation:
The headline that is an example of using standards as a trade barrier is "Only professionally cleaned oranges allowed in US." This headline implies a specific sanitary standard that imported oranges must meet in order to be sold in the US. Such standards act as a trade barrier by potentially limiting the number of imports that can meet these criteria, thereby protecting domestic industries by keeping the price of imported products higher due to the cost of meeting such standards.
When comparing to a sugar import quota, which is a limit set on the quantity of a good that can be imported (like a cap of seven tons of sugar from Brazil to the US), standards are seen as non-tariff barriers that can also affect trade flow and domestic prices.