Detailed Explanation:

Seasonal variation in day and night length occurs due to the Earth's revolution around the Sun combined with its axial tilt of 23.5°.

The tilted axis causes different hemispheres to receive varying amounts of direct sunlight throughout the year – when the Northern Hemisphere is tilted toward the Sun (summer solstice), it experiences longer days; when tilted away (winter solstice), it experiences shorter days.

❌ Option 1 – Incorrect: Earth's rotation causes the daily cycle of day and night (24 hours), not seasonal variation in their length.

❌ Option 3 – Incorrect: Latitudinal position determines the magnitude of variation (polar regions experience extreme variation, equatorial regions minimal), but not the cause of seasonal changes.

❌ Option 4 – Incorrect: The elliptical orbit affects Earth-Sun distance but does not cause seasonal day-length variation; the tilt is the primary factor.