Eutrophication is the enrichment of an ecosystem with chemical nutrients, typically compounds containing nitrogen, phosphorus, or both.
Eutrophication can be a natural process in lakes, occurring as they age through geological time.
Eutrophication was recognized as a pollution problem in European and North American lakes and reservoirs in the mid-20th century.
Human activities can accelerate the rate at which nutrients enter ecosystems.
Carbon is the atom, which is necessarily find in the living organism.
All the living organisms are made up of biomolecules. All the biomolecules are organic compounds. The substance cannot be consider as living, if it lacks nucleic acids. There are two types of nucleic acids DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), both have a structure made up of carbon rings and chains.
Other than nucleic acids, proteins, enzymes, hormones etc are also made up of carbon. So, all the living cells, or dead remain of organism must have carbon atom.
Hence, the correct answer is option D. carbon.
D. Prokaryots do not have any genetic material.