Which of the following can a transponder provide?

A transponder can provide altitude data, which is essential for air traffic control and situational awareness. Specifically, a transponder can transmit information about an aircraft's altitude as part of its Mode C or Mode S functionalities, allowing air traffic controllers to track the aircraft's vertical position accurately. This altitude reporting is crucial for maintaining safe separation between aircraft and for managing air traffic efficiently.

While other types of data, such as enemy identification or surface movement data, may also be relevant in aviation contexts, those types of information are typically provided by different systems or technologies rather than a transponder. For example, enemy identification is more aligned with military systems or radar technology, while surface movement data is usually managed by ground control and related systems that track airport movements. Weather data, on the other hand, is provided by meteorological services and not directly transmitted by transponders.