How long does it take for the moon to complete one full revolution around the Earth?

The correct answer is 27.5 days, as this is the average time it takes for the Moon to complete one full orbit around the Earth, a period known as a sidereal month.

During this time, the Moon travels through the various phases, from new to full, and back to new again. Although the lunar phases cycle approximately every 29.5 days, the orbital period itself—how long it takes to return to the same position against the background stars—is about 27.5 days.

This apparent discrepancy in time regarding the lunar phases versus the orbital period is due to the movement of the Earth around the Sun. As the Moon orbits the Earth, the Earth’s own motion means additional time is needed for the Moon to catch up and align with the Sun in terms of phases.

Understanding this orbital timing is crucial for contextualizing various phenomena involving the Moon, such as eclipses and tidal patterns. The options provided that suggest shorter or longer durations do not accurately reflect the Moon's actual orbital period relative to the Earth.