Boundaries Between Intervals of the Geological Time Scale Are Determined

Boundaries between intervals of the geological time scale are determined by

A) Climatic periods based on paleoclimatological reconstructions.
B) Major events in Earthʹs history,such as major extinctions.
C) dividing the time range of the interval by the number desired subdivisions,thereby creating equal intervals between the divisions.
D) 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.