Which of the following best describes the function of a VOR?

The function of a VOR (VHF Omni-directional Range) is best described as providing two different navigation signals. A VOR operates by transmitting a reference signal and a variable signal from the ground station. The aircraft's VOR receiver measures the phase difference between these two signals, which allows the pilot to determine the aircraft's bearing relative to the VOR station. This capability is essential for navigation, as it enables pilots to accurately orient themselves and navigate along specific flight paths.

The other available options do not correctly capture the primary function of a VOR. For instance, the measurement of distance in nautical miles is not a direct function of a VOR; that task is typically handled by other systems such as DME (Distance Measuring Equipment). Transmitting atmospheric data is outside the scope of VOR, which is focused solely on navigation assistance. Additionally, tracking real-time speed is not a function of the VOR; speed monitoring is typically achieved using other onboard instruments. Thus, option B is the most appropriate description of the VOR's capabilities.