Describe reproduction in Cyclostomata.

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

Which of the following animals lack jaws?

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:

How many gill slits are present in Cyclostomata?

$A$ group of researchers procured some fish-like animals and upon investigation the following characters were observed: $A$. Endoskeleton was made of cartilage. $B$. Ectoparasitic; as they were found attached on fish skin with their circular sucking mouth. $C$. Paired fins and scales were absent, but $7$ pairs of gill slits were present. Which of the following species of animals did they consider to fit best with these characters?