How can DME assist pilots during an approach?

The correct choice highlights how Distance Measuring Equipment (DME) is a crucial tool for pilots during an approach by enabling them to determine their distance from a specific navigational aid, such as a VOR station or an airport. This capability is vital because knowing the precise distance to the aid helps pilots manage their descent rate and stable approach, ensuring they are on the correct glide path. By providing accurate distance information, DME allows pilots to make informed decisions about their approach, including when to initiate specific maneuvers, thereby enhancing flight safety and efficiency during what is often a critical phase of flight.

In contrast, the other choices do not accurately reflect the function of DME in aviation. While real-time communication with ground staff is essential, it is not a role played by DME. Moreover, controlling engine power settings and automatically adjusting the flight path and altitude fall outside the capabilities of DME, as these functions are managed by the aircraft's systems and the pilot’s own skills.