Which of the following are intracellular obligate parasites?

Explanation

Viruses are obligate intracellular parasites because they lack the cellular structures and metabolic machinery needed to grow and reproduce independently. They cannot carry out essential life processes like energy production or protein synthesis on their own, so they must invade a host cell and hijack its machinery to replicate. In contrast, bacteria, slime moulds, and cyanobacteria are true living organisms with cellular organisation, enzymes, and metabolic pathways that allow them to survive, grow, and reproduce independently in suitable environments. This fundamental dependence on host cells for survival is what makes viruses obligate intracellular parasites, unlike bacteria, slime moulds, and cyanobacteria.