Which Method Best Describes How the Geologic Time Scale,which Was

Multiple Choice

Which method best describes how the geologic time scale,which was developed through fossil successions in sedimentary rocks,was tied to absolute time even though sedimentary rocks cannot usually be dated directly by geochronology?

A) Geologists estimated time through sedimentation rates,then using those rates together with maximum ages of underlying rocks that are datable,to extract a time interval and rate for deposition of the sedimentary rocks.
B) Geologist used things like volcanic ash beds,interbedded volcanic rocks,cross-cutting intrusive igneous rocks,etc.in sedimentary sections with a known fossil succession,and this age was extrapolated globally.
C) Geologists recently developed a technique to directly date sedimentary rocks,solving the problem.
D) Geologists realized that there were many other cosmogenic isotopes besides Carbon 14 that allow the dating of sediments,and this has allowed the dating of sedimentary rocks.