The correct answer is Earthworm.An earthworm is not a helminth which makes the drinking water unsafe.Lumbricus terrestris is the scientific name of the common earthworm.An earthworm does not have a separate head or any visible sense organ.Earthworms are generally considered beneficial to the soil, although there are times when the presence of earthworms has a negative effect.Additional InformationGuinea worm: a very long parasitic nematode worm that lives under the skin of infected humans and other mammals in rural Africa and Asia.Roundworm: a nematode worm, especially a parasitic one found in the intestines of mammals.Flatworms: a worm of a phylum that includes the planarians together with the parasitic flukes and tapeworms. They are distinguished by having a simple flattened body which lacks blood vessels, and a digestive tract which, if present, has a single opening.