Which is a unique feature of Mercury? A. It is the smallest planet and has the shortest period of revolution around the sun. B. The thick atmosphere—made mostly of carbon dioxide—absorbs solar radiation, heating up and helping make the atmosphere very hot. C. The planet’s surface is covered with red, iron-oxide dust. D. It is the only planet with permanent liquid w
A. It is the smallest planet and has the shortest period of revolution. This is true because B. is shared with Venus, C. is shared with Mars, and D. is shared with Earth, making A. the only thing unique to Mercury.
