Answer:
I'm assuming you need to label above the lines. So, above the line where the Cretaceous period ends is mass extinction and where the bracket lies is adaptive radiation.
Step-by-step explanation:
Mass extinctions are periods of time where the organisms are essentially wiped out in an extremely brief period of time. You can see how the species just drops off. Adaptive radiation occurs when there is a diversification of a group of organisms as evident by the rise in the number of marine animal groups shown by the bracketed area.