The correct option is C Viruses
Viruses are non-cellular, infectious, obligate, intracellular parasites. These are genetic elements (DNA or RNA) wrapped in a protein coat and are not considered to be organisms, as they cannot reproduce independently. Viruses contain a protein coat, known as capsid, which encloses a single type of nucleic acid, either RNA or DNA. They do not have enzymes for protein synthesis. They multiply only inside the living host cell and for multiplication, they take over the machinery of the host cell. Thus, viruses are obligatory intracellular parasites.