Which Statement About Locomotion in Nematodes Is True

Which statement about locomotion in nematodes is true?

A) Rhythmically beating cilia propel the animal forward.
B) Circular and longitudinal muscles work against each other to move the animal forward.
C) Longitudinal muscles contract to move the animal forward.
D) A series of hairs that project backward engage the substrate; back-and-forth movements move the animal forward.
E) Water expelled through specialized ducts moves the animal forward.