Which part is a fluid cavity of the earthworm that gives it a hydrostatic skeleton?
A) gut
B) coelom
C) ectoderm

Option B) Coelom

Explanation:

Hydrostatic skeleton is the type of skeleton possessed by soft-bodied animals such as earthworms and sea anemones. Fluid is secreted to fill the cavity spaces (coelom) in their body. The fluid then presses against the muscular body wall, causing the muscles to contract exerting pressure against the fluid thereby causing motion

Thus, coelom is the fluid cavity of the earthworm that gives it a hydrostatic skeleton

stress fractures occur largely in the feet and legs and are common in sports that require repetitive impact, primarily running/jumping sports such as gymnastics or track and field.