Answer:
B. Prokaryotes
Step-by-step explanation:
Spirilla are a type of bacterium that belongs to the domain Bacteria, which are prokaryotes. Prokaryotes are single-celled organisms without a nucleus or membrane-bound organelles. They have a simple cellular structure and lack the complex internal organization of eukaryotic cells. Spirilla are helical-shaped bacteria, known for their spiral shape and found in a variety of environments, such as freshwater and soil.