Give several examples of how radioactive isotopes are useful.

Radioactive isotopes are used as tracers in chemical reactions and industrial processes and in nuclear power plants. They are also used to find medical problems and treat them. They can also be used to find the ages of fossils. 

Eutrophication.

Explanation:

This is the natural process of excessive enrichment of water with nutrients by which large amount of living organic matter grows in the water.lakes slowly develop large concentration of aquatic life, which eventually decays. Human activities have speeded up this natural process of eutrophication by adding mineral and organic nutrient in larger quantities.