Which statement correctly explains seasons and the effect of Earth's tilt?

• A. The seasons are caused by the Sun's energy output varying throughout the year.
• B. Seasons happen because the Earth orbits the Sun in a perfect circle, keeping sunlight constant.
• C. Seasons are caused by daily weather patterns and have no astronomical basis.
• D. Seasons are caused by the tilt of Earth's axis, which affects the duration and intensity of sunlight in different hemispheres.

Answer: (D)

Seasons come from the tilt of Earth’s axis and how that tilt changes the angle and length of sunlight that different parts of the planet receive during the year. The axis tilts about 23.5 degrees, so as Earth orbits the Sun, the Sun’s path in the sky changes. When the Northern Hemisphere is tilted toward the Sun, days are longer and the Sun climbs higher, delivering more direct sunlight and warming that hemisphere. When it’s tilted away, days are shorter and the Sun is lower, delivering less direct sunlight and cooling. The Southern Hemisphere experiences opposite seasons at the same time. The distance from the Sun changes a bit, but that isn’t what drives the seasons; the tilt and the resulting sunlight duration and angle do.