On a Laboratory Practical Exam,you Are Presented with an Unknown

On a laboratory practical exam,you are presented with an unknown specimen.You know it either belongs to the Phylum Xenoturbellida or to the Phylum Echonodermata.What characteristic would you look for that would tell you that the specimen is from the Phylum Xenoturbellida and not the Phylum Echinodermata?

A) Bilateral symmetry
B) Diffuse nervous system
C) Endoskeleton of ossicles
D) Lack of cephalization