Which of the following best describes radar echoes associated with airborne targets?

Radar echoes associated with airborne targets are primarily characterized by clear air returns. Clear air returns refer to radar signals that reflect off of small airborne particles, such as dust, insects, or other atmospheric phenomena, rather than precipitation. These returns can provide valuable information about conditions in the atmosphere even in the absence of significant weather.

In contrast, ground clutter is the unwanted echoes received from the Earth's surface, such as buildings, trees, and other obstacles, which can interfere with the detection of airborne targets. Reflective anomalies generally refer to unexpected or unusual radar returns that do not correspond to structures or weather phenomena, making them less useful for identifying airborne targets. Pulsed radar signals denote the method by which radar systems transmit and receive signals but do not directly describe radar echoes themselves.

Thus, clear air returns offer the best understanding of how radar can detect airborne objects under certain conditions, aiding in the monitoring of air traffic and atmospheric phenomena.