A sediment core is removed from the floor of an inland sea. The sea has been in existence, off and on, throughout the entire time that terrestrial life has existed. Researchers wish to locate and study the terrestrial organisms fossilized in this core. The core is illustrated as a vertical column, with the top of the column representing the most recent strata and the bottom representing the time when land was first colonized by life.

In order to assign absolute dates to fossils in this sediment core, it would be most helpful if

A. volcanic ash layers were regularly interspersed between the sedimentary strata.
B. the sediments had not been affected by underwater currents during their deposition.
C. metamorphic rock strata alternated with sedimentary rock strata.
D. we knew the order in which the fossils occurred in the core.
E. fossils throughout the column had equal ratios of a parental radioisotope to its daughter isotope.