One of the Problems with Trying to Compute the Absolute

One of the problems with trying to compute the absolute age of Earth based on rates of accumulation of sediment is that

A) removal of salts by evaporate deposition has approximately balanced the addition of salts by rivers and other sources.
B) radioactive decay and its heat contribution to Earth's heat need to be taken into account.
C) the salinity of the world ocean may not have changed much since early in Earth's history.
D) the stratigraphic record is full of gaps and unconformities.