Aviation fuel whose anti-detonation characteristics are better than those of the reference fuel is rated in what?

The correct choice is performance numbers because this term encompasses the measurement of fuel's ability to prevent detonation as compared to a reference fuel. Performance numbers are typically used in aviation to indicate the quality and capability of fuels, especially those designed for aircraft engines, where detonation can significantly affect engine performance and safety.

While octane levels are indeed related to fuel performance and anti-knocking properties in internal combustion engines, they are a more specific measurement and do not provide the comprehensive viewpoint that performance numbers do. Fuel quality numbers and detonation indexes are also related terms but are less commonly used in the context of aviation fuel specifications. Performance numbers effectively capture the overall comparative characteristics that ensure engine efficiency and reliability in aviation fuels.