Which of the following best describes how helminths generally enter the body?

Helminths, which are parasitic worms, commonly enter the human body primarily through the ingestion of contaminated food or water. This method of transmission is especially prevalent for species such as nematodes, cestodes, and trematodes, which can have eggs or larvae that contaminate soil, food, or water sources. For example, ingestion of undercooked or raw fish infected with certain types of larvae can lead to infection, as can consuming fruits and vegetables that have been fertilized with contaminated soil.

While other routes of transmission are valid for specific parasites, they are not the primary means by which helminths generally infect humans. Contact with infected animals, while possible, is not as common for helminths compared to the fecal-oral route of ingestion. Insect bites may transmit some parasites, notably protozoa or filarial worms, but they do not typically serve as a route for the majority of helminths. Similarly, respiration of airborne eggs does not apply to helminths, as their eggs or larvae are not transmitted through the air. Thus, the ingestion of contaminated food or water stands out as the primary and most significant means of helminth entry into the human body.