Which of the following is not a class of $Tetrapoda$?

What do animals of the class Cyclostomata possess at the anterior end of their mouth?

What type of endoskeleton is found in cyclostomes?

How many gill slits are present in Cyclostomata?

Which of the following is an exclusively marine animal?

Select the incorrect statements with respect to Cyclostomes:
$(a)$ They lack scales and paired fins.
$(b)$ They have a circular mouth with jaws.
$(c)$ They bear $6-15$ pairs of gills.
$(d)$ They migrate to deep sea for spawning.
Choose the most appropriate answer from the options given below: