Which of the following is a measure used to describe astronomical distances?

Astronomical Units (AU) are specifically designed to measure distances within our solar system, based on the average distance between the Earth and the Sun. One Astronomical Unit is approximately 93 million miles or about 150 million kilometers. This unit is particularly useful in astronomy because it provides a scale that is better suited to the vast distances involved compared to conventional units like miles or meters, which can become unwieldy when discussing the distances to planets or other astronomical objects.

The other measures mentioned, while they can technically be used to describe distance, are not practical for the vast scales of space. GPS coordinates are designed for navigation on Earth and do not apply in the same way to astronomical distances. Miles and meters, though they can be converted into astronomical terms, lack the context that astronomical units provide when discussing the distances between planets or stars. Thus, Astronomical Units are the most fitting and effective measure for understanding distances in the context of astronomy.