Explain natural selection using the finches as an example.

Darwin's finches are a classical example of an adaptive radiation.Changes in the size and form of the beak have enabled different species to utilize different food resources such as insects, seeds, nectar from cactus flowers as well as blood from iguanas, all driven by Darwinian selection.

3 would be your correct It’s the portion of internal energy that can be transferred from one substance to another. (Hope this helps)