Hydrology is the science concerned with which of the following?

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Hydrology focuses on how water is distributed and moves through the Earth’s systems. It covers the movement and storage of water in all its forms—precipitation, surface water in rivers, lakes, and wetlands, groundwater, and the oceans—along with the pathways and processes that transfer water between reservoirs, such as runoff, infiltration, evaporation, and human-made structures. This broad view of where water is and how it travels is what the option describes.

The other topics belong to different fields: weather patterns are the realm of meteorology, which studies atmospheric conditions; the chemistry of salts in oceans falls under chemical oceanography or marine chemistry; the biology of aquatic organisms is studied in aquatic biology or limnology. Hydrology centers on water’s distribution and movement, tying together how water is stored and how it flows through landscapes, which is essential for understanding water supply, flood risks, and watershed management.