The correct answer is option 1, which states that the reason why the equatorial region only experiences summer year-round is because the length of day and night is more or less equal throughout the year.

Let`s dissect each option to understand why option 1 is the correct answer:

Option 1: The length of day and night is more or less equal over the year. This option is correct because the equatorial region, which lies near the Earth`s equator, experiences a consistent length of day and night throughout the year. This lack of variation in daylight hours results in a constant warm climate, giving the appearance of summer year-round.

Option 2: The Earth`s rotational velocity is maximum at the Equator. Although this statement is true, it does not explain why the equatorial region only experiences summer. The rotational velocity affects the Coriolis force and the formation of winds and ocean currents, rather than the presence of seasons.

Option 3: The Coriolis force is zero at the Equator. This statement is also true, as the Coriolis force is strongest at the poles and weakest at the equator. However, this does not directly explain the absence of seasons in the equatorial region.

Therefore, option 1 is the correct answer as it