Jacobson's organ is concerned with

Poisonous fangs of a snake are modified:

Statement $A$: The name 'Reptilia' is derived from the Latin word 'repere' or 'reptum',which means 'to creep' or 'to crawl'.
Statement $B$: Since they creep or crawl,it is not necessary that all animals of the class Reptilia are limbless.

Given below are two statements:
Statement $I$: The class name Reptilia refers to creeping or crawling mode of locomotion.
Statement $II$: All organisms belonging to Reptilia have three chambered heart.
In the light of the above statements, choose the most appropriate answer from the options given below:

To which class does the $Tautara$ (Tuatara) belong?

An animal which has both exoskeletal and endoskeletal structures is