Paleontologists hypothesize that modern birds evolved from the family

This is a "best resolves the paradox" method of reasoning type critical reasoning question. In these questions, you have to insert a piece of evidence that bridges the gap between two seemingly conflicting pieces of information. Here that information is the idea that modern birds are thought to have evolved from dinosaurs, and that fossil evidence of dinosaurs with feather-like body covering would be helpful in supporting this hypothesis yet none have been discovered.

Answer choice A is a trap and out of scope. We are simply focused on reconciling the fact that no evidence of feather-like body covering has been discovered. We are not addressing other bird-like characteristics.

Answer choice B does not help at all. Whether you want to claim dinosaurs have "died out" or not does not impact the fact that no relevant fossils have been located. This answer choice can get you thinking almost philosophically and really distract you from the issue at hand.

Answer choice C is another trap. This answer choice baits you into thinking about other bird characteristics such as flying, and is thus similar to answer choice A.

Answer choice D nails it and is thus the correct answer. If feathers do not fossilize and are therefore unlikely to leave permanent fossil records, then that would perfectly explain how the hypothesis could be correct even though these fossils have not been found.

Answer choice E is tempting, but ultimately not our most convincing choice. Even if only thousands of fossils have been excavated, it is entirely possible that every single type of dinosaur that existed has been found. There are around 7 billion humans on this planet, but you don't have to find 7 billion fossils when we die to figure out what characteristics we all share.

I hope this helps!