Which of the Following Was Not Known to Eighteenth- and Nineteenth-Century

Which of the following was not known to eighteenth- and nineteenth-century geologists?

A) Fossil organisms found in more recent strata resemble modern organisms.
B) Certain fossils are always found in younger rocks.
C) Some rocks have magnetic properties.
D) Radioactivity can be used to determine the age of rocks.
E) Fossils from more recent strata do not resemble those found in more ancient strata.