Which statement distinguishes Platyhelminthes from Nematoda?

• A. Platyhelminthes have segmented bodies; nematodes do not
• B. Both have a true coelom
• C. Platyhelminthes are acoelomates with no body cavity, while nematodes have a pseudocoelom
• D. Nematodes have a dorsal nerve cord

Answer: (C)

The main idea here is the type of body cavity each group has. Platyhelminthes are acoelomates, meaning they lack a true body cavity between the gut and the body wall. Nematoda have a pseudocoelom, a fluid-filled space between the gut and the body wall that isn’t fully lined by mesoderm, so it isn’t a true coelom.

This distinction matters because it reflects how their bodies are structured and how organs are organized within that space. The other statements don’t fit as a clear, defining difference: flatworms aren’t segmented, so that part of A isn’t correct; neither group has a true coelom (so B is incorrect); and the presence of a dorsal nerve cord isn’t the defining contrast between these two phyla.