A Sextant user must measure the [A] between two points to obtain the [B]. What do these letters represent?

In the context of using a sextant for navigation, the correct interpretation of the letters corresponds to measuring the angle between two celestial objects or a celestial object and the horizon to obtain latitude or longitude. Specifically, this involves measuring the angle created by a horizontal plane (the horizon) and a line drawn to a celestial body, which allows the navigator to determine their position on Earth.

The term "angle" pertains to the angle measured by the sextant, which is crucial in celestial navigation as it provides vital information about your position relative to the observed celestial body. This angle is essential in calculating one's latitude when observing a celestial body at its zenith or in relation to the horizon at specific times.

By accurately measuring this angle, the navigator can then interpret this data to determine their geographic coordinates, either latitude or longitude, depending on the celestial body observed and the time of observation. This is pivotal for orientation at sea, where traditional landmarks are not available.

In contrast, the other choices provide terms that do not accurately or directly relate to the primary purpose of a sextant in navigation. The sextant specifically deals with angular measurements related to celestial navigation and not with direct distances, altitudes, or other terms that deviate from its primary function.