Boundaries Between Intervals of the Geological Time Scale Are Determined

Boundaries between intervals of the geological time scale are determined by which of the following?

A) Dividing the time range of the interval by the number desired subdivisions,thereby creating equal intervals between the divisions.
B) Major events in Earth's history,such as major extinctions.
C) Using a quantile method whereby the number of years in each subdivision is determined by dividing the number of years by the desired number of classes.
D) Climatic periods based on paleoclimatological reconstructions.