Answer: C. Germ Theory
Explanation: Germ Theory states that most diseases are caused by the presence micro-organisms within the body.
Presently, it is the accepted scientific theory for many diseases.
The phylum Arthropoda contains a wide diversity of animals with hard exoskeletons and jointed appendages. Many familiar species belong to the phylum Arthropoda—insects, spiders, scorpions, centipedes, and millipedes on land; crabs, crayfish, shrimp, lobsters, and barnacles in water (Fig. 3.72).