Thermococcus, Methanococcus, and methanobacterium are:
A. Archaebacterium having eukaryotic histone homologue
B. Bacteria with the cytoskeleton
C. Archaebacterium with negatively supercoiled DNA as in eukaryotes but lacking histones.
D. Bacteria with positively coiled DNA, cytoskeleton, and mitochondria.

Hint: Archaebacteria are a gathering of microorganisms viewed as an old type of life that advanced independently from the bacteria and blue-green growth. Thermococcus, Methanococcus, and Methanobacterium are Archaebacteria.

Complete answer:
Thermococcus is a heterotroph, carefully anaerobic archaeon that develops on natural substrates, principally within the sight of basic sulfur, which is diminished to hydrogen sulfide.
-Methanococcus is a class of coccoid methanogens of the family Methylococcaceae. They are all mesophiles. Methanobacterium is a sort of Methanobacteriaceae. Now with the name standing, this class has a place not with the bacterial space but rather the archaeal area (for example, they need peptidoglycan in their cell walls).
-Methanobacterium are non-motile and live without oxygen. They have adversely supercoiled DNA. They contrast from bacteria such that they endure outrageous conditions. In contrast to bacteria, archaea cell walls don't contain peptidoglycan. Thermococcus, Methanococcus, and Methanobacterium lack histones in them. Subsequently, the right answer is choice C.
Hence, option C is correct.

Note: The significance of archaebacteria can be perceived from the accompanying focuses:
Archaebacteria have constrained the researchers to reexamine the regular meaning of species. Species are a gathering with a quality stream inside its individuals. The archaebacteria show a quality stream over its species. The cell wall is made out of Pseudomurein, which keeps archaebacteria from the impacts of Lysozyme. Lysozyme is an enzyme delivered by the safe arrangement of the host, which breaks up the cell wall of pathogenic bacteria. These don't have membrane-bound organelles, for example, cores, endoplasmic reticulum, mitochondria, lysosomes, or chloroplast.