Answer:
A. Fossil record
Explanation :
A fossil can be defined as any preserved element (e.g., bones, exoskeletons, shells, animal imprints) which can be used to demonstrate the existence of organisms from past geological periods. The totality of fossils accumulated in a particular area is referred to as the fossil record. The fossil record is very useful in geology and paleontology because the information provided by the fossils helps to place geological events and species in their corresponding geologic eras and periods.