Which of the following class is being correctly described by given statements (i - iv)?
(i) All living members of this class are ectoparasites on some fishes.
(ii) They have a sucking and circular mouth without jaws.
(iii) Circulation is of closed type.
(iv) They are marine but migrate for spawning to fresh water. After spawing, within a few days they die.

A. Cyclostomata

B. Chondrichthyes

C. Osteichthyes

D. Amphibia

Please do not use chat terms. Example: avoid using "grt" instead of "great".