Final answer:
Option (a), Dinosaurs and pterosaurs became extinct approximately 65 million years ago at the end of the Cretaceous Period, mainly due to a large meteorite impact that led to drastic environmental changes.
Step-by-step explanation:
Extinction of Dinosaurs and Pterosaurs
The extinction of dinosaurs and pterosaurs occurred approximately 65 million years ago at the end of the Cretaceous Period. This mass extinction event, often referred to as the Cretaceous-Tertiary or end-Cretaceous extinction event, led to the disappearance of all dinosaurs except for a clade of theropods that gave rise to birds. The most likely cause of this extinction was a catastrophic impact from a large meteorite or asteroid, which led to a significant alteration of the Earth’s climate and environment, drastically affecting the biodiversity at the time.
During this event, termed the "great dying," more than half of the species on the planet died out, including every land animal that weighed more than 25 kilograms. Following the extinction of dinosaurs, mammals began to diversify and eventually dominated the Earth’s land ecosystems, marking the beginning of the Cenozoic Era. This mass extinction is a crucial point in Earth's geological history and remains a subject of extensive study and fascination among paleontologists.
These prehistoric reptiles, including the flying reptiles known as pterosaurs, dominated the Earth's ecosystems for tens of millions of years throughout the Mesozoic Era, famously dubbed the "Age of the Reptiles." However, their reign ended abruptly due to the catastrophic events at the end of the Cretaceous, leading to their extinction and providing opportunities for the rise of mammals.