On which of the following do adult lampreys live as ectoparasites?

Which of the following animals are ectoparasites on fish in their adult stage?

Which of the following is present as an excretory organ in hagfish?

Ventral muscular heart,kidneys for excretion and osmoregulation,and paired appendages are found in all of the following $EXCEPT$:

Animals of this class are marine,but migrate to freshwater for spawning.

Which class is not included in the superclass $Tetrapoda$?