How does the body cavity of the frog differ from that of man?
Frog is an amphibian organism, man is a mammal. Amphibians lack a diaphragm which in mammals separate the thoracic cavity from abdominal cavity.
Thoracic cavity in mammals is guarded by ribs (no ribs are there in frog). Diaphragm is a muscular partition between thoracic and abdominal cavities, that helps in breathing.
In absence of diaphragm torso of frog has a single cavity and floor of mouth cavity in frog helps in breathing.