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

Which of the following animals belong to the class Cyclostomata?

All living members of the class Cyclostomata are:

Which animal is included in the subphylum Agnatha?

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

Which of the following statements are correct for $Cyclostomata$?
$I$ - They have a sucking and circular mouth without jaws.
$II$ - Their body is devoid of scales and paired fins.
$III$ - Their cranium and vertebral column are cartilaginous.
$IV$ - They have a closed type of circulatory system.
$V$ - $Cyclostomes$ live in freshwater, but migrate to the ocean for spawning.
$VI$ - They show direct development.