Final answer:
The profound transition in the dinosaurs occurs during the Late Jurassic period, which is considered the golden age of dinosaurs. So, the correct answer is option b.
Step-by-step explanation:
The profound transition in the dinosaurs occurs during the Late Jurassic period. The Late Jurassic period is part of the Mesozoic Era, also known as the Age of Reptiles, and is considered the golden age of dinosaurs. During this period, dinosaurs flourished and evolved, and many significant events took place, such as the evolution of the earliest birds from reptile ancestors and the diversification of mammals.
So, the correct answer is option b.