The primary cause of the seasons on Earth is a) the tilt of the Earth’s axis. This axial tilt, which is approximately 23.5 degrees, is responsible for the variations in sunlight that different parts of the planet receive throughout the year.
As the Earth orbits the sun, the tilted axis means that during different times of the year, the Northern and Southern Hemispheres are angled toward or away from the sun. For example, during the Northern Hemisphere’s summer, this part of the Earth is tilted toward the sun, resulting in longer days and more direct sunlight. Conversely, during winter, it is tilted away, leading to shorter days and less direct sunlight.
Other options like orographic uplift, Rossby waves, and Earth’s orbit around the sun play roles in weather patterns and climate, but they do not directly cause the seasons like the axial tilt does.