Answer:
The correct answer would be "Adaptive radiation happens over a relatively short time".
Adaptive radiation refers to the process of evolution in which ancestor organisms diversify rapidly into a wide variety or new forms as a result of environmental changes, availability of new resources, availability of new niches, or new challenges.
Accumulation of adaptive radiations over a long period of time results in speciation.
For example, Darwin's finches adapted according to their feeding behavior.
