The correct option is A Aschelminthes (Roundworms)
Aschelminthes are triploblastic animals having bilateral symmetry. If the body of an organism can be divided into two equal halves on cutting it in one specific plane passing through the centre, then the symmetry is called bilateral symmetry.
Triploblastic animals have all the three germinal layers - ectoderm, endoderm and mesoderm.
Ctenophores and Coelenterates (Cnidarians) are radially symmetrical and diploblastic. They can be cut in any plane passing through the centre to get equal halves and have only two germinal layers - outer ectoderm and inner endoderm.
Sponges are asymmetrical i.e., which cannot be cut in any plane to get equal halves and diploblastic.