Answer:
The right answer to this question is option A) island forms and mainland forms descended from common ancestors.
It's known in science that a long time ago, all the continents were only one, united all together in a bigger one. This can be observed by the way every continent can fit another one.
A proof of that too, is evolution, when we find organisms in an island that share some characteristics with organisms from another island, that can mean some things, they come from the same place, or these islands share characteristics that lead these organisms to be this way through evolution.
The gradual change of an organism over a period of time is called evolution.
The correct answer is A.
The difference of species is considered as the variation. The variation is due to the different habitat and nature in the surrounding. The organism in the different island is somewhat similar to each other because they had a common ancestor that separated over time and adapt themselves according to nature.
Hence, the correct answer is A that is island forms and mainland forms descended from common ancestors.
For more information, refer to the link:-
https://brainly.com/question/19524691
