This primitive fish was the ancestor of land-dwelling tetrapods (amphibians, reptiles, mammals and birds), although fish of this type still exist in the modern deep ocean:
a) jawless fish.
b) lobe-finned fish.
c) placoderms.
d) ray-finned fish.

The correct answer is option B. lobe-finned fish.

Explanation:

Lobe finned fishes or the Sarcopterygii is a group or clad of fish that contain the coelacanths, tetrapods, lungfish, and other fossil relatives. ray-finned fishes and lob finned fishes are the are sister groups.  

The major characteristic feature of this fish is the presence of lobe in their fins. The ancestral records explained that the land-dwelling tetrapods are evolved from the lobe-finned fishes around four four hundred million years ago.

Thus, the correct answer is option B. lobe-finned fish.

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