Correct option is (c) .
Dams, wells, tube wells, hand-pumps, canals, etc, are man-made sources of water. 

The correct answer is option 'A' - River.

Explanation:

Natural sources of water are bodies of water that are not man-made and occur naturally in the environment. These sources are essential for the survival of various organisms, including humans. Let's discuss each option to understand why 'River' is not a natural source of water.

1. River:
A river is a natural flowing watercourse that typically flows towards an ocean, sea, lake, or another river. While rivers are important natural sources of water, they are not themselves sources of water. Rivers are formed by the accumulation of water from various sources, such as rainfall, melting snow, and springs. Therefore, they are not considered natural sources of water.

2. Lake:
A lake is a large body of water that is surrounded by land. It is usually freshwater and can be formed by various natural processes such as tectonic activity, volcanic activity, and erosion. Lakes can also be a result of human activities like damming rivers. Lakes serve as natural reservoirs, storing water from different sources like rainfall, rivers, and groundwater.

3. Canal:
A canal is an artificial waterway constructed by humans for various purposes, such as irrigation, transportation, and water supply. Canals are man-made and are not considered natural sources of water. They are created by digging and modifying the natural terrain to redirect water from rivers or other water bodies.

4. Pond:
A pond is a small body of standing water that is usually shallow and surrounded by land. Ponds can occur naturally or can be man-made. Natural ponds are formed through various processes like glacial activity, volcanic activity, or by the accumulation of rainwater in depressions in the land. Ponds can also be created by humans for various purposes, such as irrigation or livestock watering.

In summary, while rivers are important natural watercourses, they are not considered natural sources of water. They are formed by the accumulation of water from various sources and serve as conduits for water flow. Natural sources of water include lakes, ponds, springs, and groundwater reservoirs.