Final answer:
The prokaryotic cell that is comma-shaped is referred to as vibrio, which is the correct answer among the given choices.
Step-by-step explanation:
The term that refers to a prokaryotic cell that is comma-shaped is C. vibrio. Prokaryotic cells come in various shapes and sizes, and these shapes can be used to identify different types of bacteria. A coccus is spherical, coccobacilli are short rods, spirillum are spiral shaped, and vibrio are cells that are curved or resemble a comma. Thus, when referring to a prokaryotic cell with a tight coil pattern, the correct answer is vibrio.