Answer:
The statements in options A,B,C,D and E are all correct.
A. Invertebrates lack a back bone
B. Ecdysozoans typically posses a flexible exoskeleton that protects these animals from harmful external factors like water loss.
C. Deuterstomia, Lophotrochozoa and Ecdysozoa are classes of Bilaterians.
D. Animal A is a bilateral because bilateral embryos are triploblastic possessing three germ layers, are bilaterally symmetrical and lack a back bone.
E. All animal from studies are found to have a common ancestry.
