Ill give brain thing to first answer Speciation, which leads to diversity among species through natural
selection, occurs when
Once similar species are no longer able to mate and produce fertile
offspring
Organisms develop characteristics that mimic traits of a completely
different species.
Species experience change within their lineage and develop new
characteristics.
Species interact with other species in an ecosystem and develop
similar traits to each other.

Natural selection and speciation: 'Ecological speciation'. ... Natural selection is generally recognized as a central mechanism of evolutionary change within species. Thus, natural selection plays a major role in generating the array of phenotypic and genetic diversity observed in nature.

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link:

c: warm water flows from the western tropical pacific toward south america. that should be the right answer! hope it .