Which would least likely be a cause of natural selection?

Evolution would least likely be a cause of natural selection.
Natural selection has to do with the survival of the fittest. Therefore, adaptation, variation, and overpopulation all have an impact on natural selection - those who do not adapt to their new surroundings due to overpopulation or those whose bodies have not modified enough will not survive.

1.fossils 2.analogous organs 3.homologous organs