Thermal pollution kills fish primarily because all fish need cool water fish eggs overheat fish swim too close to pipes warm water holds less oxygen

Warm water holds less oxygen

Explanation:

Thermal pollution may be defined as the cahnge in the ambient water temperature that can degrade the water quality. Main cause of thermal pollution is the use of water as coolant in industries.

Thermal pollution is harmful for aquatic life. Fish and other aquatic organismsm dies because thermal pollution increases the temperature of water. This warm water has less ability to hold oxygen and fishes die due to the lack of oxygen in water.

Thus, the correct answer is option 4.