Earth and all of the air in the atmosphere around it make up an incredibly complex system. Energy is constantly changing forms in many different ways. How would scientists most likely describe the system of the Earth in regard to energy?

Earth is an open system because energy crosses its boundary: sunlight enters the atmosphere and warms Earth, and energy also leaves as heat radiated into space. Choice B correctly identifies incoming solar energy. Earth is not isolated, and the atmosphere does not stop energy from escaping.

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