Final answer:
A region is an area of the Earth's surface with distinctive characteristics such as political, linguistic, or physical features, making answer A the correct choice.
Step-by-step explanation:
A region is an area of the Earth's surface with distinctive characteristics, which can be defined by various factors including governmental, language, political situation, or landform. In this context, the correct answer is A: An area of the Earth's surface with distinctive characteristics. Regions are an essential unit of study in geography and can range from formal countries and physical landforms to areas defined by cultural practices and economic functions. This term does not refer to the Earth's atmosphere, which is the gaseous area surrounding the planet, nor is it a naturally occurring phenomenon in itself, but rather a conceptual area defined by humans for the purpose of geographic study.
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