A group of scientists wants to test the effects of increased salinity on a population of catfish in a river. what result from this experiment would confirm that natural selection is a process that can drive evolution?

The catfish that survive must have been born with an adaptation to the increase of salt in their fresh water environment. The remaining catfish would then be able to reproduce and the new catfish would have the same trait. Eventually the whole population will have this trait which would drive evolution.