Correct Option (d)
The Earth's axis is tilted at an angle of approximately 23.5 degrees relative to its orbital plane. As the Earth revolves around the Sun, this constant axial tilt causes different hemispheres to receive varying durations of direct sunlight throughout the year. This phenomenon is the primary reason for seasonal changes and the observed variations in the length of daytime and nighttime from one season to another. For example, during the summer solstice, a hemisphere experiences its longest day, while during the winter solstice, it experiences its shortest day.
Incorrect Options
(a) The Earth's rotation on its axis is responsible for the daily cycle of day and night. However, it does not account for the seasonal variations in their respective lengths, as the rotation period remains constant.
(b) While the Earth's orbit around the Sun is elliptical, the slight variation in distance from the Sun has a negligible impact on the seasonal changes in day and night lengths compared to the effect of the axial tilt.
(c) The latitudinal position of a place influences the general duration and intensity of sunlight received. However, it is not the fundamental cause of the seasonal variation in day and night lengths. This variation is primarily driven by the Earth's axial tilt in conjunction with its revolution around the Sun.