The body of the phylum ________ is unsegmented and dorsoventrally flattened.
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. Platyhelminthes.
- The flatworms, or phylum *Platyhelminthes*, have an unsegmented, dorsoventrally flattened body.
- Since they don't have a specialised respiratory system, their flattened shape provides a huge surface area for gas exchange.
- Both free-living species like planarians and parasitic species like tapeworms and flukes are classified as flatworms.
- They frequently live as parasites or in watery habitats, therefore their basic body form is an adaptation to their way of existence.