What is the last phase of the Moon before it becomes a New Moon?

The last phase of the Moon before it transitions into a New Moon is the Waning Crescent phase. During this phase, the illuminated portion of the Moon is decreasing, with only a small crescent of light visible just prior to the Moon becoming completely dark. The transition from a Full Moon to a New Moon involves several phases, with the Waning Crescent being the final visible phase as the Moon's illumination declines. This progression is important in understanding the lunar cycle and how the changing positions of the Moon, Earth, and Sun affect what we observe from our perspective on Earth.

In contrast, the Full Moon occurs earlier in the lunar cycle when the Moon is fully illuminated, while the Waning Gibbous phase indicates that the Moon is still more than half illuminated but decreasing. The Third Quarter phase shows half of the Moon illuminated, still prior to the Waning Crescent. Each of these phases follows the Full Moon but does not occur directly before the New Moon, making the Waning Crescent the correct answer.