Which of the following could be considered the most recent common ancestor of living tetrapods? a) a sturdy-finned, shallow-water lobe-fin whose appendages had skeletal supports similar to those of terrestrial vertebrates b) an armored, jawed placoderm with two pairs of appendages c) an early ray-finned fish that developed bony skeletal supports in its paired fins d) a salamander that had legs supported by a bony skeleton but moved with the side-to-side bending typical of fishes

a) a sturdy-finned, shallow-water lobe-fin whose appendages had skeletal supports similar to those of terrestrial vertebrates.

Explanation:

An ancestor - An earlier type of a species at any distant time — a progenitor.

A tetrapod is any vertebrate with four limbs. It includes any vertebrate (such as birds or snakes) that have evolved from early tetrapods — especially all members of the superclass Tetrapoda.

The presence of bones that support the appendages in Lobe – fin fish were found to be similar to the categorical skeletal supports found in the limbs of sample tetrapods. The sub class crossopterygii includes the Lobe – fin fish, which is seen as one of the recent common ancestor of living tetrapod today.

answer: a. a gene that causes a specific trait.

thinking it would be physical characteristics