A 13-year-old boy from India was brought to the emergency room with a prolapsed rectum. Examination of the rectum reveals small worms that resemble whips attached to the mucosa. A stool sample reveals eggs that are barrel shaped, with bipolar plugs. Which of the following is the most likely cause?

  •   Entamoeba histolytica
  •   Echinococcus granulosus
  •   Enterobius vermicularis
  •  Ascaris lumbricoides
  •   Trichuris trichiura
  •   Giardia lamblia