Individual birds have different colored feathers. Island finches have a large number of offspring. Individual birds of an island finch species have many differences. Island finches share a common ancestry with mainland finch species.
I gave my students this multiple choice question: Charles Darwin made a number of observations and inferences during his travels. He studied island finches during a long period of time. Which statement is an inference?

Only one answer is correct among these 4 choices:
- Individual birds have different colored feathers.
- Island finches have a large number of offspring.
- Individual birds of an island finch species have many differences.
- Island finches share a common ancestry with mainland finch species.

Could you tell me which one is correct?

Island finches share a common ancestry with mainland finch species.