The correct option is D Viruses
PPLO is a prokaryotic cell that lacks a cell wall and is distinguished as mycoplasma. Rickettsia and archaebacteria are also bacterial species that are known to be as prokaryotic cells. All the prokaryotes have a cell structure that includes nucleus, Golgi apparatus and ribosomes. prokaryotes survive in nature on their own or inside the body of the host. Viruses, on the other hand, lacks cellular structure and only consists of the genetic material which is multiplied by using host cell machinery (eg. they use ribosomes of host cells for translation of viral mRNA into proteins). Viruses do not multiply on their own and need a host to replicate themselves due to lack of cellular structure. Hence, option C is correct.