Answer:
The correct answer is option A. Bacterium.
Explanation:
Any organism that lacks a true or proper nucleus and other cellular organelles because of the absence of internal membranes are characterized as prokaryotic cells and such organisms are call prokaryotic organisms.
the bacterium is a unicellular microorganism that has cell walls but lacks an organized nucleus and cellular organelles, which is a character of the prokaryotic organism. Bacteria make a large group or domain of prokaryotes.
Thus, the correct answer is option A.
