During the Earth's complete revolution around the sun, the most significant event that occurs is that four seasons occur on Earth. This is because the tilt of the Earth's axis relative to its orbit around the sun causes variations in sunlight, leading to the changing seasons.
While the Earth does experience day and night during this time (as it rotates on its axis), the focus of the question regarding a complete revolution is more aligned with the concept of seasons. The moon's phase changes are not directly tied to the Earth's orbit around the sun in the same way.
So, the best answer is: Four seasons occur on Earth.