Final answer:
The statement that all dinosaurs reproduced by laying eggs is A. true. Fossilized eggs and embryos, along with research on modern-day reptiles and birds, support the oviparous nature of dinosaurs.
Step-by-step explanation:
The statement that all dinosaurs reproduced by laying eggs is true. Dinosaurs, like their reptilian relatives, are known to have laid amniotic eggs, which are characterized by an array of protective membranes. Fossilized eggs and even embryos of dinosaurs have provided evidence supporting that they reproduced through oviparous (egg-laying) methods. Additionally, the similarity in reproductive strategies between modern birds and reptiles, both of which lay eggs and share a common ancestor with dinosaurs, further substantiates this understanding.
Notably, a significant discovery by paleontologists, including Mark Norell, has identified soft eggshell material around dinosaur embryos dating back over 200 million years. All this fossil evidence, coupled with our understanding of the reproductive systems in modern-day reptiles and birds, points to the conclusion that dinosaurs were indeed egg layers.