When do spring tides occur?

Spring tides occur during the full moon and new moon phases. This is when the Earth, moon, and sun are aligned, causing the gravitational forces of the sun and moon to combine, resulting in the highest high tides and the lowest low tides.

During the full moon, the moon is on the opposite side of the Earth from the sun, while during the new moon, the moon is positioned between the Earth and the sun. In both situations, the gravitational pull is reinforced, leading to more extreme tidal ranges.

In contrast, the other lunar phases, like the first and last quarter moons, do not have this alignment, and thus do not produce the same tidal effects as the spring tides. Therefore, the timing of spring tides is specifically associated with these two phases, making the answer C the correct choice.