Most of what we know about dinosaurs is based on

A. molecular data

b. similarities in embryos

c. vestigial organs

d. fossils

The correct answer would be D. Molecular data could only do us good with carbon dating and perhaps genetic info. We have no living examples of dinosaur embryos, only fossils. It is very rare for vestigial organs to be fossilized. Fossils tell us about size, stature, anatomy, diet, and a slew of other things.