When is adaptive radiation most likely to occur and for what reasona- after a mass extinction , because the survivors give rise to species that fill new inches b- just before a mass extinction , because species are competing intensely for limited resources c- when the climate is warmest, because high temperatures act to increase the rate of evolutionary changed- when the climate is stable , because a stable environment tends to decrease the rate of evolutionary change

a- after a mass extinction , because the survivors give rise to species that fill new inches  

Explanation:

Adaptive radiation is a phenomenon that refers to the process in which there occurs an enhanced diversity of organisms and old specie give rise to the evolution of a diverse array of new species.

The process of adaptive radiation can occur under special circumstances for example, when there occurs a change in environment in such a way that  there are more environmental resources to sustain new organisms.

There is a famous example of Adaptive radiation that is finch speciation on the Galapagos that was well studied and researched by Darwin.

Here are the conditions under which adaptive radiation can occur:

In view of above facts, option A is best option.

Hope it help!

the second type of galaxy is called a barred spiral, which has a thing called a bar straddling the nucleus