Explanation:

*Archaeopteryx* is a genus of bird-like dinosaurs that lived in the Late Jurassic period, about $150$ million years ago. It is considered a transitional fossil, exhibiting characteristics of both reptiles and birds, providing strong evidence for the evolution of birds from feathered dinosaurs. It had reptilian features like teeth, a long bony tail, and claws on its wings, alongside avian features like feathers and a furcula (wishbone). Option (B) is correct because *Archaeopteryx* serves as a crucial connecting link, demonstrating evolutionary relationships between reptiles and birds. Options (A), (C), and (D) are incorrect as *Archaeopteryx* does not bridge the evolutionary gap between reptiles and mammals, amphibians and reptiles, or birds and mammals.