Concept:Bilateral symmetry, a cylindrical body, and two separate openings (mouth and anus) point to an organism with a complete digestive tract.
Explanation:Nematodes are bilaterally symmetrical, meaning they can be split lengthwise into two mirror-image halves.
They have a cylindrical body shape.
Nematodes possess a complete digestive system called an alimentary canal, giving them two openings: a mouth and an anus.
In contrast, hydra has radial symmetry and a single opening that serves as both mouth and anus.
Protozoans and protists are mostly unicellular and generally lack true double openings.
Therefore, the given features are characteristic of nematodes.
Answer:A. nematodes