Question

the hydrostatic skeleton of the earthworm allows it to move around in its environment by
alternating contractions and relaxations of its smooth muscle.
crawling with its feet.
swimming.
walking on its limbs.
using peristaltic contractions of its circular and longitudinal muscles.

Explanation:

Earthworms move through peristaltic contractions of circular and longitudinal muscles in their hydrostatic - skeleton system. They don't have feet, limbs, and don't swim in the traditional sense. Smooth muscle contractions are not the main way for their movement.

Answer:

using peristaltic contractions of its circular and longitudinal muscles.