Ants benefit by getting the sugary food from the aphid and aphids benefit because the over crowding of ants on the aphid protects them from their predator just as lady beetles and flies. What type of relationship is this? Competition
Mutualism
Commensalism
Parasitism

mutualbecausen they get benefit from each others

Any preserved remains, trace, or impression of any once-thriving living thing from the past geological age is known as a fossil. This comprises exoskeletons, bones, stone imprints of animals or microbes, shells, hair, petrified wood, objects preserved in amber, DNA remnants, coal, and oil. The fossil record is the term used for the totality of fossils.  

The scientists use the prevailing fossils to show what the intermediary forms between the organisms may appear like. It is hard for the scientists to locate the fossils of the transitional forms as the formation of the fossils of the transitional forms may have never taken place because of the environmental conditions. In case if they did have formed, then the natural procedures like erosion may have demolished them.