Refer to the given dichotomous key and select the correct option regarding it.
I. (A) Animal shows radial symmetry - Go to II
(B) Animal shows bilateral symmetry - Go to III
II. (A) Acoelomate animal - P
(B) Coelomate animal - Q
III. (A) Anus develops prior to mouth in the embryo - R
(B) Mouth develops prior to anus in the embryo - S
AP could be Spongilla that reproduces asexually by formation of gemmule.
BQ could be Ophiothrix having body surface covered by mesodermal endoskeleton of calcareous spines.
CR could be Dugesia having an incomplete digestive tract.
DS could be Milvus that respires through lungs.
Do all organisms which respire through lungs are deuterostomes