Question

Elasmobranchii comes under the class of
A. Bony fishes
B. Cartilaginous fishes
C. Lung fishes
D. L – lag fish

Answer 1

Hint:- Fish are abundant in water bodies. They may be found in nearly all aquatic zones, from high mountain streams to the abyssal and even hadal depths of the deepest oceans, Even no species has been seen in the deepest 25% of the ocean. 34,300 well-known species of fish represented noble species diversity than any other group of vertebrates.

Complete step-by-step solution:-
The class Chondrichthyes is also known as cartilaginous fish which contain sharks, skates, and sawfish. This class is divided into two subclasses Elasmobranchii and Holocephali. These fishes are jawed vertebrates and their skeletons are composed of cartilage instead of bone, and their heart is chambered so we can say that Elasmobranchii in the class of cartilaginous fishes. Most of the elasmobranchs are found in marine water but various known species are also found in freshwater, only sixty well-known species among 1154 are found in freshwater. They are divided into two groups; euryhaline elasmobranchs and obligated freshwater elasmobranchs. Euryhaline elasmobranchs are marine water species but they can also live and reproduce in freshwater while the obligated freshwater elasmobranchs can only live and reproduce in freshwater.
As per the above explanation, the correct answer to this question is option B, and I hope you guys will make sure why other options are incorrect.

Note:- The immunoglobulins or antibodies were first evolved in cartilaginous fish. The existence of an IgM-like antibody permits for the first time not only particular B cell-mediated effector functions but also the complete formation of complement activation pathways.