Astronomy Practice Exam 2025 - Free Astronomy Practice Questions and Study Guide

The term "waning crescent" refers to a specific phase of the moon that occurs after the last quarter phase and just before the new moon. During this phase, the moon appears as a small, thin sliver of light that is decreasing in size. Even though "waning" suggests a diminishing light, more importantly, it signifies that the moon is transitioning towards a phase where it is nearly invisible, which aligns with option A.

In this context, the moon's visibility is minimal as it approaches the new moon phase, where it would be completely obscured. A waning crescent is typically seen just before it vanishes from sight, making the interpretation of nearly invisible accurate for this phase.

The other choices do not accurately reflect the characteristics of the waning crescent phase. The fully illuminated moon describes the full moon phase, while a growing moon refers to the waxing phases, which are completely opposite to how the waning crescent behaves. Thus, the essence of a waning crescent is indeed a phase where the moon moves toward being nearly invisible.