Aheat source could be considered a source of pollution

Yes, it is called as thermal pollution

Thermal pollution can be defined as the degradation of the quality of water by any processes that are known to change the water temperature.

As the temperature of water bodies increases, the green algae may be replaced by cyanobacteria. One of the main problems with thermal pollution is the replacement of cold water fishes with the warm water.

Industrial factories and power plants are the main contributors of thermal pollution

The warm water changes the metabolism pattern of the fishes, it increases their metabolism, which leads to malnutrition as a result of that all the fishes die. Warm water also depletes the dissolved oxygen and increases the level of bacteria. It will result in abundant of nutrients, will lead to overpopulation of aquatic life. As a result of increased algal growth, other aquatic animals are not able to grow because of a lack of photosynthesis, they die because of a lack of oxygen, which will pollute the marine environment.

the answer to your question is:

c. complementary base-pairing