The correct answer is C. Spirilla.
Bacteria are classified into three main shapes: cocci, bacilli, and spirilla. Cocci are round or spherical bacteria, bacilli are rod-shaped bacteria, and spirilla are spiral-shaped bacteria.
Spirilla are long, thin bacteria that are often corkscrew-shaped. They are typically motile, meaning that they can move around on their own. Spirilla are found in a variety of environments, including soil, water, and the human body. Some species of spirilla are beneficial, while others can cause disease.
For example, the bacterium Helicobacter pylori, which is spiral-shaped, is a common cause of stomach ulcers. However, there are also beneficial spiral-shaped bacteria, such as those that live in the human gut and help to digest food.
Bacteria are important organisms that play a vital role in the environment. They are also important for human health, as they are used to produce antibiotics and other medications.