Which of the following terms is recognized by the EU as a quality indicator for Portuguese wines?

The term "Reserva" is recognized by the EU as a quality indicator for Portuguese wines, specifically indicating a higher quality level for wines that have met certain aging and production criteria. In Portugal, wines labeled as "Reserva" must meet specific standards, including a minimum aging period, which varies depending on the type of wine. This designation is often associated with greater complexity, depth of flavor, and overall quality, making it a useful indicator for consumers seeking higher-quality Portuguese wines.

In contrast, "Cabernet" refers to a grape variety and does not inherently convey quality specific to Portuguese wines. "Vinho Regional" identifies wines produced in specific geographic regions within Portugal but does not automatically denote quality; it merely indicates the wine's origin. "Vinho Verde" signifies a distinct wine style from a particular region in Portugal and does not serve as a quality indicator in the same way that "Reserva" does. Thus, "Reserva" stands out as the correct answer due to its association with quality standards within the EU regulations for Portuguese wines.