What is the purpose of the geologic time scale?
A. to organize and sequence events by eras and periods in the different divisions of time and to serve as a timeline
B. to show the evolution of life forms and to model how those life forms behaved and what they ate
C. to organize and sequence events in the history of Earth and to serve as a model for a vast amount of time covered
D. to determine the relative ages of rocks and when and how they formed to create a timeline of their development