A key derived character of sharks and rays that distinguishes them from ray-finned fishes is
A) jaws and a swim bladder.
B) vertebrae.
C) calcified (hard) bones.
D) a skeleton made of cartilage

Jaws and a swimming bladder

Explanation:

A defining characteristic between sharks and rays that distinguish them from ray-finned fish is the *possession of jaws in sharks* and rays;and the *possession of swimming bladder in ray-finned fishes*.

Characteristics of sharks and rays are as follows :

They are cartiiliginous fishes; they possess *strong jaws* lined with teeth; body dorsoventrally flattened, fusiform (spindle shaped) with heterocercal tail(diphycercal in Chimaeras); paired fins; *no swimming bladder or lungs*; pelvic fins in males often modified to form clappers; Gill arches internal to gills; reduced notchord; lateral-line system; paired nostrils; internal nares absent; separate sexes; internal fertilization and direct development; oviparous, oviparous, or ovoviviparous. Examples include, Spiny dog fish or dog shark, Ray Raja, Chimaera.

Characteristics of ray-finned fishses:

They generally lack paired fins; no internal nares; *air sacks usually function as swimming bladder*; skeleton usually well ossified. Blind olfactory sacs (do not open into the mouth); Tail homocercal. Examples include Tilapia, Claris,and Polypterus.

it has one origin of replication, but it proceeds in two directions - d)

explanation:

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