Which of the following is the best source of fresh water?

Correct option is D

The correct answer is (D) River
Explanation:
A river is considered one of the primary and best sources of accessible fresh water. Unlike oceans and seas, river water has very low concentrations of dissolved salts (usually less than 1%).
Most rivers are fed by precipitation (rain), melting snow, or glaciers. This water flows over the land, providing a vital source for drinking, irrigation, and industrial use.
Of that small percentage, rivers, lakes, and streams represent the most easily accessible portion compared to water trapped in glaciers or deep underground.
Information Booster:
While rivers are excellent sources, the largest reservoir of fresh water on Earth is actually held in glaciers and ice caps (about 68.7%), followed by groundwater (about 30.1%).
Rivers are part of the hydrological cycle, where water is constantly redistributed through evaporation, condensation, and precipitation.
Additional Knowledge:
Ocean and Sea (Options A & B)

Oceans and seas contain saline water. On average, ocean water has a salinity of about 35 parts per thousand (35‰), meaning every 1 kg of water contains 35 grams of dissolved salts (mostly sodium chloride).
This water cannot be consumed directly by humans or used for most agriculture without expensive desalination processes.
Salt water (Option C)
This is a general term for water with high salt content (like that found in oceans). Approximately 97% of Earth's water is salt water, making it the most abundant but least usable form for direct human consumption.