The answer is D.) Indirect sunlight striking Earth
The main cause of winter is the fact of Earth being tilted on its axis. Winter occurs when light rays coming from the sun hit Earth's surface at a lower angle which results in less energy being transferred to the surface of the planet because of the glancing characteristics of the sun's rays. This results from indirect sunlight striking Earth. Since the Northern and Southern hemispheres are tilted away from each other, their seasons will always be different from one another.
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