Correct Option: D

Roundworms, or nematodes, are a group of invertebrates (animals having no backbone) with long, round bodies. Most parasitic roundworm eggs or larvae (immature form) are found in the soil and enter the human body when a person picks them up on the hands and then transfers them to the mouth. The eggs or larvae also can enter the human body directly through the skin. With the exception of the parasitic roundworm that causes trichinosis, mature adult roundworms eventually end up or live in human large intestines and cause infection and disease.