Question

which bacterial form can be curved like a spiral, thick and rigid, or thin and flexible?
○ spirillum
○ coccus
○ bacillus
○ aerobic

Explanation:

To solve this, we analyze each option:

• spirillum: Spiral - shaped bacteria. Some spirilla are thick/rigid (spirillum), others thin/flexible (spirochetes, a type of spirillum - like form).
• coccus: Spherical bacteria, not spiral.
• bacillus: Rod - shaped bacteria, not spiral.
• aerobic: Relates to oxygen use, not a bacterial form.

So spirillum matches the description.

Answer:

A. spirillum