Agnatha includes:

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:

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

Jawless vertebrates are placed in the group .........

Petromyzon attaches itself to the host body with the help of:

Circular and sucking mouth is found in . . . . . . .