Answer:
Option D, hydroskeleton
Step-by-step explanation:
The hydro skeleton is structure which is commonly found in the animals that have soft body with fluid filled cavity. This fluid in the cavity exerts pressure on the surrounding muscles which help an organism to change its body shape or move. These organism generally move by contracting and expanding their body . Some example of animals possessing hydrostatic or hydroskeleton are star fish, earthworms etc.