Answer: The correct answer is-
Coccus bacteria.
Bacteria are unicellular, prokaryotic organisms that is they are made up of single cell and lack nucleus and membrane bound organelles.
Based on their structures, they exist in primarily three shapes that are-
1) Coccus ( cocci for plural)-The cocci are round/spherical or oval shaped bacteria.
Example- Streptococcus pyogenes, Staphylococcus aureus
2) Bacillus ( bacilli for plural)- They cylindrical/ rod shaped or capsule like bacteria.
Example- E.coli.
3) Spirullum ( spirulli for plural) - They are spiral shaped bacteria.
Example- Spirillum volutans.