Which statement best describes the organism referred to as a flatworm in the given material?

Which statement best describes the organism referred to as a flatworm in the given material?

• A. Platyhelminthes are flatworms
• B. Nematoda are flatworms
• C. Annelida are flatworms
• D. Echinodermata are flatworms

Answer: (A)

Flatworms are named for their flattened bodies, and the group that embodies this form is Platyhelminthes. So the statement that Platyhelminthes are flatworms is the best description because it directly links the common name to its scientific name. In other words, flatworm describes what members of Platyhelminthes look like and how they are organized. This phylum includes both free-living planarians and parasitic tapeworms and flukes, all sharing a flattened body plan and a simple digestive system, typically without a true body cavity. The other options refer to different phyla with distinct body plans: roundworms (Nematoda) have a tubular body and a pseudocoelom, segmented worms (Annelida) have true segments and a coelom, and echinoderms (Echinodermata) are radially symmetric marine animals with a water vascular system.

Flatworms are named for their flattened bodies, and the group that embodies this form is Platyhelminthes. So the statement that Platyhelminthes are flatworms is the best description because it directly links the common name to its scientific name. In other words, flatworm describes what members of Platyhelminthes look like and how they are organized. This phylum includes both free-living planarians and parasitic tapeworms and flukes, all sharing a flattened body plan and a simple digestive system, typically without a true body cavity. The other options refer to different phyla with distinct body plans: roundworms (Nematoda) have a tubular body and a pseudocoelom, segmented worms (Annelida) have true segments and a coelom, and echinoderms (Echinodermata) are radially symmetric marine animals with a water vascular system.