Final answer:
Cocci are spherical, bacilli are rod-shaped, and spirilli are spiral-shaped. All three categories have a cell wall, plasma membrane, and ribosomes, while bacilli and spirilli often have flagella and pili for movement and attachment.
Step-by-step explanation:
Prokaryotes are broadly classified into three distinct shapes: cocci, spirilli, and bacilli. Cocci are spherical or ball-shaped bacteria, commonly found in pairs (known as diplococci), clusters (like staphylococci), or chains (as in streptococci). On the other hand, spirilli are spiral-shaped and often have a twisted form, which can range from a simple helix to a more complex shape. Lastly, bacilli are rod-shaped bacteria, either occurring singly or in chains. Despite their different shapes, all three categories have certain structural features in common, such as a cell wall, a plasma membrane, and ribosomes.
Bacilli and spirilli typically have flagella for locomotion and pili for attachment. However, these structures may vary among species or be absent in certain types of bacteria, like some cocci. Additionally, all prokaryotic cells have a nucleoid region containing genetic material, as they lack a true, membrane-bound nucleus.
The correct option is B.