It has mountains, plains, and depressions that cast shadows.
Explanation
The Moon is Earth's only natural satellite. Its surface characteristics are defined by its geological history and the lack of a significant atmosphere.
Analysis of Options:
- It has water and air essential for life. is incorrect: The Moon does not have air (atmosphere) or liquid water on its surface, which are essential conditions for life. While traces of water ice have been found in permanently shadowed craters, the surface environment is hostile to life.
- It is perfectly smooth without any depressions. is incorrect: The lunar surface is not smooth. It is heavily scarred with impact craters, rugged mountains, and vast plains known as maria.
- It has mountains, plains, and depressions that cast shadows. is correct: The Moon has a diverse topography comprising steep mountains, flat plains (maria), and deep depressions (craters). These physical features obstruct sunlight, casting long shadows that are visible from Earth, especially near the terminator line (the division between day and night on the Moon).
- It emits its own light during the night. is incorrect: The Moon is a non-luminous body. It does not emit its own light; instead, it shines by reflecting sunlight.
Key Takeaway: The Moon is a non-luminous satellite with a rugged surface featuring mountains, plains, and craters, lacking the atmosphere and water necessary to support life.