What is the main characteristic of the hydrosphere?

The main characteristic of the hydrosphere is that it includes all forms of water on Earth. This encompasses not only the saltwater found in oceans but also freshwater in rivers, lakes, glaciers, groundwater, and atmospheric moisture such as water vapor and precipitation. The hydrosphere plays a crucial role in supporting life, regulating climate, and influencing geological processes.

In contrast, the other options do not accurately define the hydrosphere. The hydrosphere is not limited to atmospheric gases, as it primarily focuses on water in its various states. While solid landforms belong to the lithosphere, they do not represent the hydrosphere. Additionally, limiting the hydrosphere to freshwater bodies excludes a significant portion of Earth's water, which is mainly saline and located in the oceans. Thus, recognizing the hydrosphere as encompassing all forms of water is essential for understanding its role in Earth's systems.