The answer is b) Prokaryotic organisms are always unicellular.
Explanation for each option:
a) Prokaryotic organisms can be either unicellular or multicellular - This statement is incorrect. Prokaryotic organisms, such as bacteria and archaea, are always unicellular. They do not form multicellular organisms.
b) Prokaryotic organisms are always unicellular - This statement is correct. Prokaryotic organisms are single-celled organisms without a nucleus or other membrane-bound organelles.
c) Eukaryotic organisms are always unicellular - This statement is incorrect. Eukaryotic organisms can be either unicellular (like yeast) or multicellular (like humans, plants, and animals).
d) Eukaryotic organisms are neither unicellular nor multicellular - This statement is incorrect. Eukaryotic organisms can be either unicellular or multicellular, depending on the species.
In summary, prokaryotic organisms are always unicellular, while eukaryotic organisms can be either unicellular or multicellular.