Question

multiple choice question
what occurred at the end of the cretaceous period?
o the \age of amphibians\ began
o mass extinction of dinosaurs that opened up habitats
o first appearance of mammals and birds
o mass extinction, in which gymnosperms and angiosperms disappeared

Explanation:

At the end - Cretaceous mass - extinction event, dinosaurs went extinct, which opened up ecological niches. Mammals and birds did not first appear then, and gymnosperms and angiosperms did not disappear completely. The "Age of Amphibians" predated the Cretaceous.

Answer:

mass extinction of dinosaurs that opened up habitats