The correct option is A Dog fish
Elasmobranchii (dog fish) is an alternative name for cartilaginous fish or chondrichthyes. The name refers to the fact that the gill-slits are exposed and not covered by an operculum. Dog fish or scoliodon is a true fish whereas silver fish is arthropods, star fish is echinoderms and whale is a mammal. Thus, the correct answer is option A.