Terry saved some of the tooth-like objects within the hagfish's round mouth to analyze their composition in his mentor's biochemistry research lab. Terry will find that they are composed of the same protein found in tetrapod .a. scalesb. bonesc. teethd. cartilage

The correct answer is option a. "scales".

Explanation:

The missing information of this question is the following:

"Terry catches a ray-finned fish from the ocean and notices that attached to its flank is an equally long, snakelike organism. The attached organism has no external segmentation, no scales, a round mouth surrounded by a s*cker, and two small eyes. Terry concludes it is a hagfish."

Gymnophiona is a group of amphibians characterized by having dermal scales as integumentary element. These amphibians are tetrapods and their scales are comprised of several layers of unmineralized collagenous fibers. The skeleton of the hagfish is made entirely of cartilage, therefore it is very likely that the tooth-like objects of hagfish's are made of cartilage, just like the scales of the tetrapod.