What are the 3 major groups of eubacteria?

• A. Spirilla
• B. Cocci, Bacilli, Spirilla
• C. Vibrios
• D. Bacilli, Spirilla, Vibrios

Answer: (B)

Bacteria are commonly classified by shape into three broad forms: cocci (spherical), bacilli (rod-shaped), and spirilla (spiral). This shape-based approach is a fundamental way to categorize eubacteria and helps quick identification under a microscope. The option that lists cocci, bacilli, and spirilla includes one representative of each major shape, making it the best choice. The other options mix in shapes that aren’t part of the standard three-group framework—spirilla alone doesn’t cover all three, vibrios are curved rods and not one of the core three shapes, and a set that includes vibrios but omits cocci would miss a major category.