Consider following statements and Choose correct ones from given options. I. Shark do not have any bone in its body. II. Water snake and salamander belongs to same class and have largest RBC. III. Silver fish is a true fish while cuttle and star fishes are molluscs and echinoderms respectively. IV. Ornithorhynchus is a connecting link between reptiles and mammals.

Step-by-step solution

- Shark is a member of Chondrichthyes class, which is a cartilaginous fish. - Water snake is a reptile and salamander is an amphibian having largest RBC in animal kingdom. - Silver fish (Lepisma) is an arthropod, cuttle fish (Sepia) is a mollusc and star fish (Asterias) is an echinodermate. So none of them is a true fish (Pisces). - Ornithorhychus is a mammal which is also known as duck-billed playtypus. It is a member of Monotremata order which is a connecting link between reptiles and mammals.