Animals can be divided into several classes or phyla, each of which has specific characteristics that allow classification.
The cnidarians have as main representatives the jellyfish, they have radial symmetry;
Roundworms are bilaterally symmetrical and triploblastic roundworms;
Sponges are animals that have no tissues and are not symmetrical;
Ctenophores are small animals often with radial symmetry.
Analyzing the options we can say that the answer is the alternative "B) Roundworms".
