On which of these do the phases of the moon have an affect?

a.the season
b.ocean tide
c.day and night
d.weather

The correct answer is b. ocean tide.

To understand why the phases of the moon affect ocean tides, we need to consider the gravitational force between the Moon, Earth, and water bodies on Earth. The Moon exerts a gravitational pull on the Earth, causing the water on the side of the Earth closest to the Moon to bulge outward, forming a high tide. At the same time, the water on the opposite side of the Earth also bulges outward due to the centrifugal force caused by the Earth-Moon system's rotation. This creates another high tide, known as the "opposite high tide."

When the Moon is at its fullest or new phase, the gravitational pull of the Moon and the Sun align, creating higher high tides known as spring tides. On the other hand, when the Moon is in its first or third quarter phase, the gravitational pull of the Moon and the Sun partially cancels out, resulting in lower high tides known as neap tides.

Therefore, the phases of the Moon have a direct impact on the height of ocean tides. However, it is worth noting that the phases of the Moon do not directly affect the other options mentioned in your question: a. the seasons, c. day and night, and d. weather.